Sub-pascal unidirectional flow valves

ABSTRACT

A valve includes a body including an inner bore extending between a first port and a second port, a seat, and one or more restrainers and a disk that is moveable between the seat and the one or more restrainers such that a first pressure that is less than 1 pascal and applied in a first direction causes the disk to move from a first position towards a second position to permit fluid communication between the first port and the second port. A metamaterial scaffold including a structure defining a lumen, at least a portion of an outer or non-lumen surface of the structure is coated with a plurality of biological cells, and wherein the structure is composed of a metamaterial.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. ProvisionalApplication No. 62/696,077, filed on Jul. 10, 2018, and U.S. ProvisionalApplication No. 62/844,471, filed on May 7, 2019, each of which ishereby incorporated by reference herein in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

This invention was made with government support under Grant No.EEC-1647837 awarded by the National Science Foundation. The governmenthas certain rights in the invention.

TECHNICAL FIELD

The present disclosure relates generally to valves, and moreparticularly, to valves for use with fluidic systems or devices.

BACKGROUND

Some fluidic systems or devices operate at low pressures. These systemsor devices often use a valve to control the flow (e.g., unidirectionalflow) of fluid to freely permit fluid flow, completely inhibit fluidflow, or achieve a predetermined flow rate. While some valves, such ascheck valves, automatically open and close responsive to application ofa predetermined pressure in a given direction, these valves cannotoperate at low pressures because the low pressure is insufficient tocause movement of the internal plug or disk that controls flow. Thus, influid flow systems or devices operating at low pressures (e.g., lessthan 1 pascal), valve(s) typically need to be controlled manually suchthat the valve(s) open/close responsive to an input (e.g., a signal froma controller) rather than open/close automatically in response toapplication of a predetermined pressure.

The structural organization and mechanical properties of theextracellular environment can critically affect cellular properties andtissue organization. This is emphatically the case for cardiac tissue,where the highly anisotropic extracellular matrix can affect thealignment, the contractile performance and the cellular andintracellular structure of cardiomyocytes. Nevertheless, attempts tocontrol and exploit the extracellular environment to enhance tissues invitro fall short primarily due to the lack of techniques that canproduce such environment with sufficient resolution

The present disclosure is directed to solving these and other problems.

SUMMARY

According to some implementations of the present disclosure, a valvecomprises a body including an inner bore extending between a first portand a second port, a seat, and one or more restrainers and a disk thatis moveable between the seat and the one or more restrainers such that(i) a first pressure that is less than 1 pascal and applied in a firstdirection causes the disk to move from a first position towards a secondposition to permit fluid communication between the first port and thesecond port and (ii) a second pressure that is less than 1 pascal andapplied in a second opposing direction causes the disk to move from thesecond position towards the first position to inhibit fluidcommunication between the first port and the second port.

According to some implementations of the present disclosure, a valve foruse in a microfluidic system comprises a body including an inner boreextending between a first port and a second port, a seat having anopening and being disposed within the inner bore, and a plurality ofrestrainers positioned between the seat and the second port, and a diskthat is moveable relative to the seat and the plurality of restrainerssuch that application of a first predetermined pressure that is betweenabout 0.05 pascals and 1 pascal causes the disk to move from a firstposition towards a second position to permit fluid communication betweenthe first port and the second port.

According to other implementations of the present disclosure, ametamaterial scaffold comprises (i) a structure defining a lumen; (ii)at least a portion of an outer or non-lumen surface of the structurecomprises a layer of biological cells, and wherein the structure iscomposed of a metamaterial.

According to additional implementations of the present disclosure, amicrofluidic device comprises the cylindrical metamaterial scaffold andthe valve described herein.

The above summary is not intended to represent each embodiment or everyaspect of the present invention. Additional features and benefits of thepresent invention are apparent from the detailed description and figuresset forth below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of a valve according to someimplementations of the present disclosure;

FIG. 1B is a top view of the valve of FIG. 1A according to someimplementations of the present disclosure;

FIG. 1C is a perspective cross-sectional view of the valve of FIG. 1Aaccording to some implementations of the present disclosure;

FIG. 2A is a partial cross-sectional side view of the valve of FIG. 1Awith a disk in a first position according to some implementations of thepresent disclosure

FIG. 2B is a zoomed-in view showing portions of the disk and seat of thevalve of FIG. 2A according to some implementations of the presentdisclosure

FIG. 2C is a partial cross-sectional side view of the valve of FIG. 1Awith a disk in a second position according to some implementations ofthe present disclosure;

FIG. 2D is a zoomed-in view showing portions of the disk and seat of thevalve of FIG. 2C according to some implementations of the presentdisclosure;

FIG. 3A is a graph showing exemplary pressure values for causing thevalve of FIGS. 1A-2D to move from the first position to the secondposition and vice versa according to some implementations of the presentdisclosure;

FIG. 3B is a graph showing alternative exemplary pressure values forcausing the valve of FIGS. 1A-2D to move from the first position to thesecond position and vice versa according to some implementations of thepresent disclosure;

FIG. 4A illustrates exemplary simulated von Mises stress and fluidvelocity values during movement from the first position (FIGS. 2A-2B) tothe second position (FIGS. 2C-2D) according to some implementations ofthe present disclosure;

FIG. 4B illustrates exemplary simulated von Mises stress values andfluid velocity during movement from the second position (FIGS. 2C-2D) tothe first position (FIGS. 2A-2B) according to some implementations ofthe present disclosure;

FIG. 5A is a graph showing simulated valve transition times versusdifferent dimensional values of the disk of the valve of FIGS. 1A-2Daccording to some implementations of the present disclosure;

FIG. 5B is a graph showing simulated displaced volume per cycle versusdifferent dimensional values of the disk of the valve of FIGS. 1A-2Daccording to some implementations of the present disclosure;

FIG. 6A is a cross-sectional view of a valve including a hinge accordingto some implementations of the present disclosure;

FIG. 6B is another cross-sectional view of the valve of FIG. 6A showinga pin of the hinge according to some implementations of the presentdisclosure;

FIG. 7 is a top view of a micro-cardiac device, a first valve, and asecond valve according to some implementations of the presentdisclosure;

FIG. 8A is a perspective view of the micro-cardiac device of FIG. 7during a first fabrication step according to some implementations of thepresent disclosure;

FIG. 8B is a perspective view of the micro-cardiac device of FIG. 7during a second fabrication step according to some implementations ofthe present disclosure;

FIG. 8C is a perspective view of the micro-cardiac device of FIG. 7during a third fabrication step according to some implementations of thepresent disclosure;

FIG. 8D is a perspective view of the micro-cardiac device of FIG. 7during a fourth fabrication step according to some implementations ofthe present disclosure;

FIG. 8E is a perspective view of the micro-cardiac device of FIG. 7during a fifth fabrication step according to some implementations of thepresent disclosure;

FIG. 8F is a perspective view of the micro-cardiac device of FIG. 7during a sixth fabrication step according to some implementations of thepresent disclosure;

FIG. 9A is a perspective assembled view of a micro-cardiac device, afirst valve, and a second valve according to some implementations of thepresent disclosure;

FIG. 9B is a perspective exploded view of the micro-cardiac device,first valve, and second valve of FIG. 9A according to someimplementations of the present disclosure;

FIG. 10 is a graph showing exemplary flow rate values versus exemplarypressure values for the valve of FIGS. 1A-2D according to someimplementations of the present disclosure;

FIG. 11A is a graph showing exemplary flow rate values versus times forthe valve of FIGS. 1A-2D at a first pulsatile cross-valve pressurefrequency according to some implementations of the present disclosure;

FIG. 11B is a graph showing exemplary flow rate values versus times forthe valve of FIGS. 1A-2D at a second pulsatile cross-valve pressurefrequency according to some implementations of the present disclosure;

FIG. 11C is a graph showing exemplary flow rate values versus times forthe valve of FIGS. 1A-2D at a third pulsatile cross-valve pressurefrequency according to some implementations of the present disclosure;

FIG. 11D is a graph showing exemplary flow rate values versus times forthe valve of FIGS. 1A-2D at a fourth pulsatile cross-valve pressurefrequency according to some implementations of the present disclosure;

FIG. 12A shows a unit cell of an inverted hexagon in contraction (left)and expansion (right) according to some implementations of the presentdisclosure;

FIG. 12B shows an interconnected inverted hexagon lattice forming anauxetic structure in contraction (left) and expansion (right) accordingto some implementations of the present disclosure;

FIG. 12C shows a rotating square unit cell in contraction (left) andexpansion (right) according to some implementations of the presentdisclosure;

FIG. 12D shows an interconnected rotating square lattice forming anauxetic structure in contraction (left) and expansion (right) accordingto some implementations of the present disclosure;

FIG. 12E shows a star based auxetic lattice in contraction (left) andexpansion (right) according to some implementations of the presentdisclosure;

FIG. 12F shows a rotating triangle auxetic lattice in contraction (left)and expansion (right) according to some implementations of the presentdisclosure;

FIG. 13 is a top view of a microfluidic device comprising a first valve,a second valve and a cylindrical scaffold according to someimplementations of the present disclosure;

FIG. 14 is a top view of a microfluidic device comprising a first valve,a second valve and a cylindrical scaffold according to someimplementations of the present disclosure;

FIG. 15A shows a portion of a micro-cardiac device with cardiac tissueone day after seeding according to some implementations of the presentdisclosure;

FIG. 15B shows the cardiac device of FIG. 15A seven days after seedingaccording to some implementations of the present disclosure;

FIG. 16A shows a hollow cylindrical construct based on an invertedhexagon cell unit according to some implementations of the presentdisclosure;

FIG. 16B shows a detailed view of the cylindrical construct of FIG. 16Aaccording to some implementations of the present disclosure;

FIG. 17A shows an auxetic mesh under compression during ananoindentation test according to some implementations of the presentdisclosure;

FIG. 17B shows a plot of the force-displacement data for ananoindentation test according to some implementations of the presentdisclosure;

FIG. 18A shows an initial microfluidic device without the metamaterialscaffold according to some implementations of the present disclosure;

FIG. 18 B shows a detailed view of the microfluidic device according tosome implementations of the present disclosure;

FIG. 18C shows the placement of an auxetic construct in the microfluidicdevice according to some implementations of the present disclosure;

FIG. 18D shows the insertion of a needle into the microfluidic deviceaccording to some implementations of the present disclosure;

FIG. 18E shows the addition of cell containing liquid to themicrofluidic device according to some implementations of the presentdisclosure;

FIG. 18F shows the formation of a cell-laden layer around the needleaccording to some implementations of the present disclosure;

FIG. 18G shows the removal of the needle according to someimplementations of the present disclosure;

FIG. 18H shows sealing of the redundant channels in the microfluidicdevice according to some implementations of the present disclosure; and

FIG. 18I shows the completed device according to some implementations ofthe present disclosure.

While the disclosure is susceptible to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and will herein be described in detail. Itshould be understood, however, that it is not intended to limit theinvention to the particular forms disclosed, but on the contrary, theintention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the invention as defined by theappended claims.

DETAILED DESCRIPTION

Many fluidic systems or devices, including micro-fluidic systems ordevices (e.g., that operate at sub-millimeter scales), operate at lowpressures such as, for example, pressures that are less than 1 pascal,pressures between about 0.5 pascals and about 0.05 pascals, etc. Thesesystems and devices often use one or more valves to control the flow offluid within the system or device. For example, the valve(s) can be usedto inhibit or prevent fluid flow, freely permit fluid flow, or toprecisely control the flow rate. Some valves (e.g., check valves)include an internal disk or plug that automatically opens to permitfluid flow responsive to a first predetermined pressure being applied ina first direction and automatically closes to inhibit fluid flowresponsive to a second predetermined pressure being applied in a secondopposing direction. However, these valves cannot operate at lowpressures (e.g., less than 1 pascal) because the pressure isinsufficient to cause movement of the internal plug or disk.

Referring generally to FIGS. 1A-1C, a valve 100 includes a body 110 anda disk 130. As described in further detail herein, the disk 130 ismoveable relative to the body 110 responsive to application of apredetermined pressure that is, for example, less than 1 pascal. Thevalve 100 can generally be used, for example, in a fluidic (e.g.,microfluidic) system to control fluid flow direction and rectification.

The body 110 has a generally cylindrical shape and includes an innerbore 112 extending therethrough. More specifically, as shown in FIG. 1C,the inner bore 112 extends between a first port 114 and a second port116. As described in further detail herein, fluid can flow through theinner bore 112 between the first port 114 and the second port 116 whenthe disk 130 is an open position. The inner bore 112 is generallycylindrical and has an inner diameter that is less than an outerdiameter of the body 110 (e.g., such that a ratio of the inner diameterto the outer diameter is ¾). While the body 110 and the inner bore 112are both shown and described herein as being cylindrical, moregenerally, the body 110 and/or the inner bore 112 can have any othersuitable shape or profile (e.g., a rectangular profile, a squareprofile, a triangular profile, or a polygonal profile).

As shown in FIG. 1C, the body 110 includes a seat 120 that is disposedwithin the inner bore 112. The seat 120 has an annular shape andprotrudes or extends from an inner surface of the inner bore 112. Theseat 120 has an opening 124 with a diameter that is less than thediameter of the inner bore 112. The opening 124 permits fluid flowbetween the first port 114 and the second port 116 through the seat 120.The body 110 also includes a plurality of restrainers 122A-122D thatextend or protrude from the inner bore 112 and are positioned betweenthe opening 124 of the seat 120 and the second port 116. As shown, eachof the plurality of restrainers 122A-122D have a general “L” or “gamma”shape. Given their relative position in the inner bore 112, theplurality restrainers 122A-122D restrict or inhibit movement of the disk130 such that the disk 130 is only moveable between the opening 124 ofthe seat 120 and the plurality of restrainers 122A-122D during operationof the valve 100. While the plurality of restrainers 122A-122D is shownas including four restrainers, the body 110 can more generally includeany suitable number of restrainers (e.g., one, two, three, six, ten,etc.) and shapes to inhibit disk 130 from moving towards the second port116 during operation of the valve 100.

In some implementations, the body 110 also includes a plurality ofalignment members 126A-126H (FIGS. 1B and 1C) protruding or extendingfrom the inner bore 112. Each of the plurality of alignment members126A-126H are interspersed or positioned between a pair of the pluralityof restrainers 122A-122D or is positioned directly underneath theplurality of the restrainers 122A-122D. For example, as shown in FIGS.1B and 1C, a first alignment member 126A is positioned between a firstrestrainer 122A and a fourth restrainer 122D, a second alignment member126B is positioned under the first restrainer 122A, a third alignmentmember 126C is positioned between the first restrainer 122A and a secondrestrainer 122B, a fourth alignment member 126D is positioned under thesecond restrainer 122B, a sixth alignment member 126E is positionedbetween the second restrainer 122B and the third restrainer 122C, asixth alignment member 126F is positioned under the third restrainer122C, a seventh alignment member 126G is positioned between the thirdrestrainer 122C and the fourth restrainer 122D, and an eight alignmentmember 126H is positioned under the fourth restrainer 122D. Theplurality of alignment members 126A-126H generally aid in positioning(e.g., centering) the disk 130 over the opening 124 of the seat 120 sothat the disk 130 can inhibit flow through the inner bore 112 betweenthe first port 114 and the second port 116 during operation of the valve100 responsive to the disk 130 being a closed position. As shown in FIG.1C, each of the plurality of alignment members 126A-126H have agenerally rectangular shape, although other shapes and/or profiles arecontemplated (e.g., triangular, circular or semi-circular, polygonal,etc.). Moreover, while the plurality of alignment members 126A-126D isshown as having four alignment members (e.g., the same as the number ofthe plurality of restrainers 122A-122D), the plurality of alignmentmembers 126A-126H can more generally include any suitable number ofalignment members for aligning (e.g., centering) the disk 130 duringoperation of the valve 100 (e.g., one, two, three, six, ten, etc.)

As shown in FIG. 1C, the disk 130 is generally positioned between theseat 120 and the plurality of restrainers 122A-122D. As describedherein, the disk 130 is moveable relative to the rest of the valve 100.Because the disk 130 has a diameter that is greater than the diameter ofthe opening 124 of the seat 120, and because of the relative position ofthe plurality of restrainers 122A-122D, the disk 130 cannot move pastthe seat 120 and/or the plurality of restrainers 122A-122D duringoperation of the valve 100. That is, movement of the disk 130 isconfined to a predetermined area or portion of the valve 100 defined bythe seat 120 and the plurality of restrainers 122A-122D. The pluralityof alignment members 126A-126H aid in aligning (e.g., centering) thedisk 130 over the opening 124 of the seat 120 during operation of thevalve 100.

Referring to FIGS. 2A and 2B, the disk 130 is shown in a first or closedposition. As shown, in the first position, a portion of the disk 130contacts the seat 120 (e.g., covers the opening 124 and/or extends orprotrudes into the opening 124) such that fluid cannot flow from thefirst port 114 past the disk 130. As shown in FIG. 2B, the disk 130includes a cylindrical portion 132 and a spherical portion 134. Aportion of the spherical portion 134 is disposed within or protrudesinto the opening 124 of the seat 120 to inhibit fluid from flowing pastthe disk 130 in either direction through the inner bore 112. The shapeof the spherical portion 134 aids in maintaining sufficient contactbetween the seat 120 and the disk 130 to inhibit fluid flow in case oflateral displacement of the disk 130 relative to the opening 124. In thefirst position, an upper surface of the cylindrical portion 132 of thedisk 130 is spaced from a lower surface of each of the plurality ofrestrainers 122A-122D (e.g., restrainer 122D as shown in FIG. 2B) by afirst distance d₁.

Referring to FIGS. 2C and 2D, the disk 130 is shown in a second or openposition. As shown, in the second position, the disk 130 is spaced fromthe seat 120 such that fluid can flow through the opening 124 and pastthe disk 130 (e.g., such that fluid can flow from the first port 114 tothe second port 116 through the inner bore 112. In the second position,the upper surface of the cylindrical portion 132 of the disk 130 isspaced from a lower surface of each of the plurality of restrainers122A-122D (e.g., restrainer 122D as shown in FIG. 2B) by a seconddistance d₂ that is less than the first distance d₁. While the disk 130is shown as being spaced from both the seat 120 and the plurality ofrestrainers 122A-122D in the second (open) position in FIGS. 2C and 2D,in some implementations, the upper surface of the disk 130 is in contactwith the lower surface of the plurality of restrainers 122A-122D whenthe disk 130 is in the second position.

The disk 130 automatically moves during operation of the valve 100 fromthe first position (FIG. 2A) to the second position (FIG. 2C) inresponse to application of a first predetermined pressure in a firstdirection (e.g., from the first port 114 towards the second port 116),which causes a pressure differential between the first port 114 and thesecond port 116, to permit fluid to flow through the inner bore 112between the first port 114 and the second port 116. Similarly, the disk130 of the valve 100 automatically moves during operation of the valve100 from the second position (FIG. 2C) to the first position (FIG. 2A)in response to application of a second predetermined pressure in asecond opposing direction (e.g., from the second port 116 towards thefirst port 114), which causes a pressure differential between the firstport 114 and the second port 116, to inhibit or prevent fluid flowthrough the inner bore 112 between the first port 114 and the secondport 116. In some implementations, the first predetermined pressureand/or the second predetermined pressure are less than about 1 pascal.Generally, the first predetermined pressure and/or the secondpredetermined pressure can be between about 0.01 pascals and about 1pascal, between about 0.05 pascals and 0.75 pascals, between about 0.05pascals and about 0.5 pascals, etc. The absolute value of the firstpredetermined pressure can be the same as, or different than, theabsolute value of the second predetermined pressure. For example, theabsolute value of the first predetermined pressure can be greater thanthe absolute value of the second predetermined pressure, or vice versa.

Referring to FIG. 3A, a graph showing exemplary first/secondpredetermined pressure differential values for causing the disk 130 tomove from the first position (FIG. 2A) to the second position (FIG. 2C)or vice versa according to one implementation of the valve 100 is shown.In the example of FIG. 3A, the first predetermined pressure (pressuredifferential) for causing the disk 130 to move from the first position(FIG. 2A) to the second position (FIG. 2C) (e.g., to permit fluid flow)is between about 0.4 pascals and about 0.8 pascals (e.g., about 0.4pascals, about 0.38 pascals, about 0.31 pascals, about 0.25 pascals,about 0.22 pascals, about 0.18 pascals, etc.). As shown, the secondpredetermined pressure, for causing the disk 130 to move from the secondposition (FIG. 2C) to the first position (FIG. 2A) (e.g., to inhibitfluid flow), is less than the first predetermined pressure values and isgenerally between about, for example, 0.13 pascals and about 0.06pascals (e.g., about 0.13 pascals, about 0.11 pascals, about 0.08pascals, about 0.06 pascals, etc.)

Referring to FIG. 3B, a graph showing alternative exemplary first/secondpredetermined pressure differential values for causing the disk 130 tomove from the first position (FIG. 2A) to the second position (FIG. 2C)or vice versa according to some implementations of the valve 100 isshown. In a first implementation of the valve 100, the firstpredetermined pressure and the second predetermined pressure are bothabout 0.2 pascals. In a second implementation of the valve 100, thefirst predetermined pressure is about 0.2 pascals and the secondpredetermined pressure is about 0.08 pascals. In a third implementationof the valve 100, the first predetermined pressure is about 0.23 pascalsand the second predetermined pressure is about 0.13 pascals.

Referring to FIG. 4A, an image showing exemplary von Mises stress andfluid velocity values during movement of the disk 130 from the firstposition (FIGS. 2A-2B) to the second position (FIGS. 2C-2D) according toone exemplary, non-limiting implementation of the valve 100 is shown. Inthe example of FIG. 4A, a 0.1 pascal pressure differential is applied toopen the valve 100 (move the disk 130 from the first position towardsthe second position) and the disk 130 automatically stops moving towardsthe second position after traveling a distance of about 20 microns.Referring to FIG. 4B, a graph showing exemplary von Mises stress valuesand fluid velocity values during movement of the disk 130 from thesecond position (FIGS. 2C-2D) to the first position (FIGS. 2A-2B)according to one exemplary, non-limiting implementation of the valve 100is shown. In the example of FIG. 4B, a −0.1 pascal pressure differential(applied in the opposite direction as the 0.1 pascal pressure in FIG.4A) causes the valve 100 to close (move the disk 130 from the secondposition towards the first position) with the disk 130 starting about 20microns away from the seat 120.

The dimensions of one or more of the components of the valve 100 can beselected to adjust the properties and/or performance of the valve 100.For example, an outer diameter of the body 110 and a diameter of theinner bore 112 can be selected to provide a sufficient thickness of thebody 110 for mechanical robustness. As another example, a distancebetween the first port 114 and a lower surface of the seat 120 (FIG. 1C)can be selected to minimize the distance between the disk 130 and thepressure source. As a further example, a thickness or height of thecylindrical portion 132 (FIG. 2B) of the disk 130 and/or a degree ofcurvature of the spherical portion 134 (FIG. 2B) of the disk 130 can beselected to improve contact (e.g., coaptation) between the disk 130 andthe seat 120 when the disk 130 is in the first position (FIG. 2A) and/ormechanical robustness of the disk 130. A diameter of the disk 130 (thatwill be less than the diameter of the inner bore 112) can be selected toimprove contact (e.g., coaptation) between the disk 130 and the seat 120when the disk 130 is in the first position (FIG. 2A) and/or minimizeresistance to fluid flow when the disk 130 is in the second position(FIG. 2C). A distance between the upper surface of the seat 120 and alower surface of each of the plurality of restrainers 122A-122D can beselected to permit sufficient fluid flow when the disk 130 is in thefirst position (FIG. 2A) and to permit short transition times. Foranother example, a distance between the outer surface of opposing onesof the plurality of alignment members 126A-126D (e.g., between alignmentmembers 126A and 126C or between alignment members 126B and 126D) can beselected to minimize spacing to improve alignment (e.g., centering) ofthe disk 130. In some implementations, a diameter of the opening 124 ofthe seat 120 is equal to twice the diameter of the disk 130 minus thediameter of the inner bore 112.

In one non-limiting, exemplary implementation of the valve 100, theouter diameter of the body 110 is 400 microns, the length or height ofthe body 110 is 1100 microns, the diameter of the inner bore 112 is 300microns, the distance between the first port 114 and the lower surfaceof the seat 120 is 100 microns, the degree of curvature of the sphericalportion 134 (FIG. 2B) of the disk 130 is 50 degrees, the thickness orheight of the cylindrical portion 132 (FIG. 2B) of the disk 130 is 7microns, the diameter of the cylindrical portion 132 of the disk 130 is260 microns, the height of the spherical portion 134 (FIG. 2B) of thedisk 130 is 29 microns, the distance between the upper surface of theseat 120 and the lower surface of each of the plurality of restrainers122A-122D is 65 microns, and the distance between opposing ones of theplurality of alignment members 126A-126D is 275 microns.

While the disk 130 has been shown and described herein as having acylindrical portion 132 and a spherical portion 134 (FIG. 2B), moregenerally, the disk 130 can have any suitable shape (or a combination ofshapes) for inhibiting flow through the opening 124 of the seat 120 whenthe disk 130 is in the first position (FIGS. 2A and 2B). For example, insome implementations, the disk 130 does not include the cylindricalportion 132. As another example, in other implementations, the disk 130has a generally conical portion that is disposed within or protrudesinto the opening 124 to inhibit fluid flow.

Referring generally to FIGS. 5A and 5B, a series of simulation of thefunction of valve 100 under bipolar pulsatile pressure (1 Hz, 0.1 Pa)using different dimensions are illustrated. FIG. 5A illustrates valvetransition time (seconds) versus different values for the degree ofcurvature (θ) of the spherical portion 134 (FIG. 2B) of the disk 130 andthe radius (d₂/2) of the cylindrical portion 132 (FIG. 2B) of the disk130. The opening valve transition time is the time that it takes for thedisk 130 to move from the first position (FIG. 2A) to the secondposition (FIG. 2C). Conversely, the closing valve transition time is thetime that it takes for the disk 130 to move from the second position(FIG. 2C) to the first position (FIG. 2A). As shown, theseopening/closing valve transition times were simulated for various valuesfor the degree of curvature θ of the spherical portion 134 (e.g., 30°,50°, 70°, 90°, 110°, 130°, 150°, 180°) and various values of the radius(d₂/2) of the cylindrical portion 132 (e.g., 110 microns, 120 microns,130 microns, 140 microns). FIG. 5B illustrates displaced volume percycle (μL) versus different values for the degree of curvature (θ) ofthe spherical portion 134 (FIG. 2B) of the disk 130 and the radius(d₂/2) of the cylindrical portion 132 (FIG. 2B) of the disk 130.

Referring to FIG. 10, a graph illustrating exemplary flow rate values(μL/s) versus exemplary pressure differential values (Pa) for the valve100 under a range of positive (opening the valve) and negative (closingthe valve) pressure differential values is shown. The dots represent theacquired data and the black line represents a linear fit using a leastsquares method. The graph of FIG. 10 illustrates that the closed state(e.g., when the disk 130 of the valve 100 is in the first position (FIG.2A)) exhibits two orders of magnitude higher resistance to fluid flow.

Referring generally to FIGS. 11A-11D, a series of graphs illustratingexemplary flow rate values (Ws) versus time (seconds) for a plurality offrequencies are shown. FIGS. 11A-11D show the temporal profile of theflow rate of fluid (e.g., water) through an exemplary implementation ofthe valve 100 (FIGS. 1A-2D) described herein. A pulsatile cross-valvepressure in the form of a square pulse between −50 Pa and 50 Pa wasapplied at different frequencies across FIGS. 11A-11D. In FIG. 11A,frequency value is 1 Hz. In FIG. 11B, the frequency value is 2 Hz. InFIG. 11C, the frequency value is 3 Hz. In FIG. 11D, the frequency valueis 4 Hz. The graphs show that the fluid flow is rectified towardsnegative values in all frequencies, with transition times less than 100ms.

Referring to FIGS. 6A and 6B, a valve 200 that is similar to the valve100 (FIGS. 1A-2D) described herein is shown. The valve 200 is similar tothe valve 100 in that the valve 200 includes a body 210 and a disk 230that are similar to the body 110 and the disk 130 described herein. Thebody 210 includes a seat 220 with an opening 224 that is the same as, orsimilar to, the seat 120 and the opening 124 of the valve 100. While thedisk 230 is shown and described herein as having a generally cylindricalor generally circular shape, other shapes that are suitably for coveringthe opening 224 are contemplate (e.g., rectangular, square, oval,triangular, polygonal, etc.)

The disk 230 differs from the disk 130 of the valve 100 in that the disk230 includes a hinge 232 that is coupled to a first mounting portion222A and a second mounting portion 222B of the seat 220. The hinge 232rotates about a horizontal axis to cause the disk 230 to move relativeto the opening 224 of the seat 220. Specifically, as shown in FIG. 6B,the hinge 232 includes a cylindrical pin 234 that is received within anaperture in each of the first mounting portion 222A and the secondmounting portion 222B of the seat 220 to permit rotation of the hinge232 relative to the seat 220. As shown in FIGS. 6A and 6B, the disk 230is a second position that is similar to the second position of the disk130 described herein (FIG. 2C) in that the disk 230 being in the secondposition permits fluid to fluid through the opening 224 in eitherdirection. To inhibit or prevent fluid from flowing through the opening224, the disk 230 is moveable to a first or closed position that is thesame as or similar to the first position of the disk 130 (FIG. 2A) inthat the in the first position, the disk 230 inhibits fluid flow throughthe opening 224.

Like the disk 130 of the valve 100 (FIGS. 1A-2D), the disk 230 ismoveable between the first position and the second position responsiveto a pressure differential across the opposing ends of the disk 230.That is, the disk 230 is moveable from the first position towards thesecond position responsive to application of a first predeterminedpressure differential in a first direction, and moveable from the secondposition towards the first position responsive to application of asecond predetermined pressure differential in a second opposingdirection. The first predetermined pressure differential and/or thesecond predetermined pressure differential for the valve 200 can be thesame as, or different than, the first and/or second predeterminepressures of the valve 100 described herein.

Exemplary Fabrication Methods

The valves described herein (e.g., valve 100 or valve 200) can generallybe manufactured or fabricated using any suitable technique or method,such as, for example, photolithography, two-photon laser lithography,stereolithography, or reactive ion etching. While techniques likephotolithography and stereolithography have higher throughput, thesetechniques generally have lower resolution than two-photon laserlithography techniques.

Two-photon direct laser writing (TDPLW) can reliably and reproduciblygenerate features with resolution of less than 1 micron, and it allowsthe valves described herein to be fabricated as a single process even inembodiments where the disk is not physically tethered to the body (e.g.,like the disk 130 of the valve 100). That is, in implementationsutilizing two-photon laser lithography, all of the components of thebody 110 of the valve 100 are unitary and/or monolithic, and the disk130 is manufactured concurrently or simultaneously with the body 110.The two-photon laser lithography process can use, for example, IP-Dipphotoresist available from Nanoscribe GmbH of Stutensee, Germany, whichallows for high printing resolution, high elastic modulus, high yieldstress and high mechanical resilience even at high fluid pressures andimpact forces.

As described above, in some implementations, the disk 130 includes aspherical portion 134 (FIG. 2B). To fabricate the spherical portion 134with a high throughput, droplets of the desired material can be cast ona flat substrate (e.g., a silicon wafer). Electrowetting or coating(e.g., silanization, spin coating, vapor deposition, etc.) of the flatsubstrate can be used to control the contact angle between the monomersolution and the flat substrate to reproducibly define the degree ofcurvature of the spherical portion 134. The volume or amount of castmaterial solution can control the overall size of the final radius ordegree of curvature and the size of the plate. The material droplets arethen solidified to form the final part. As described in further detailherein, additional layers or bulk blocks of a different type of materialcan be added on the substrate and be encapsulated by the cast liquiddroplet, or can be deposited (e.g., using vapor deposition,electroplating, sputtering, coating, etc.) on the solidified droplet.The independent fabrication of the disk allows access to materials notcompatible with standard photolithography requirements and that would beeroded by the processes in photolithography protocols, and also allowsprocessing of the disk without affecting the other features of thevalve.

As a further alternative method, reactive ion etching can be used tofabricate the components of the valve (e.g., valve 100 and/or valve200), where each component can be fabricated using the choice of asuitable eroding mask.

Exemplary Valve Component Materials

In addition to the materials described above (e.g., IP-Dip photoresist),the valves described herein (valve 100 and/or valve 200) can compriseone or more materials that provide additional functionality. Forexample, in some implementations, the disk 130 can comprise apiezoelectric material (e.g., a piezoelectric disk, a piezoelectric diskstack, a bimorph, etc.) that cam modify, in situ, the geometry of thedisk 130 responsive to application of an external signal (e.g., anexternal electric field). Modification of the geometry of the disk 130using a piezoelectric material can be used to, for example:

-   -   modify the flow resistance of the valve by changing the lateral        and vertical spacing of the valve as a function of the external        signal (e.g., as a function of an external electrical field        intensity)    -   modify the efficacy of the contact (e.g., coaptation) between        the disk 130 and the seat 120    -   modify the transition time, dead volume, and/or transition        pressure between the open (first position) and closed (second        position) states    -   inhibit (e.g., completely prevent) fluid flow even when the disk        130 is in the open state (second position) and as an        implementation of a close switch    -   permit fluid flow even when the disk 130 in the closed state        (first position) as an implementation of an open switch by, for        example, impairing the coaptation efficiency between the disk        and the seat

In some implementations, the valves described herein can comprise amagnetic material (e.g., magnetic nanoparticles scattered within thedisk 130, a piece(s) of magnetic material embedded in or completelymaking up the disk 130, magnetic coating deposited/developed on thedisk, etc.) External magnetic actuators (e.g., permanent magnets orelectromagnets) can be used to induce a magnetic field to, for example:

-   -   Dynamically actuate the disk 130 between the first position and        the second position, rendering the valve an active valve (e.g.,        similar to a solenoid valve) instead of a passive pressure check        valve    -   Apply a predetermined force to the disk 130, biasing its        position towards the closed state (first position) or open state        (second position), and thus modifying the transition pressure

In some implementations, the valves described herein can comprise alight modulated material (e.g., completely making up or coatingconsisting an appended piece on the disk 130) to modify the geometry ofthe disk 130 in the same or similar manner as described above for thepiezoelectric material implementations. In some implementations, thevalves described herein can comprise a swelling material (e.g., pH orosmotically induced swelling) to control the geometry of the disk, or tomodify the stiffness of the disk 130. In some implementations, thevalves described herein can comprise a degradable material (e.g.,induced by pH, a chemical reagent added within medium, etc.) to modifythe geometry or stiffness of the disk 130. In other implementations, thevalves described herein can comprise a thermally expanding material tomodify the geometry of the disk 130.

In some implementations, the valves described herein can include one ormore materials that coat or fully comprise the disk 130, the seat 120,the plurality of alignment members 126A-H, and/or the plurality ofrestrainers 122A-D to modify the mechanical and/or chemical propertiesof the valve. For example, the seat 120, the plurality of restrainers122A-D and/or the disk 130 can comprise a soft elastic material toimprove coaptation efficiency and diodicity of the valve, as well asresilience to chronic wear, deformation, high pressures and impactforces between the disk 130, the seat 120 and the plurality ofrestrainers 122A-D upon closing (transition to first position) andopening (transition to second position) of the valve. Such soft elasticmaterials include, for example, conformal coating (e.g., parylene),kPa-MPa elastic modulus hydrogels and elastomers (e.g., polyethyleneglycol based polymers or 4-hydroxybutyl acrylate). Using these softelastic materials can decouple the coaptation efficiency from thegeometrical resolution of the fabrication technique, and thus permitlower resolution fabrication methods (e.g., stereolithography, extrusionprinting).

Similarly, in some implementations, the surface of any or all of thevalve components can be coated with a hydrophilic or a hydrophobic layerto improve interaction with the hydrophilic or hydrophobic fluid, or toinhibit or reduce adhesion of contaminants in the fluid to the valve.These hydrophilic or hydrophobic coatings can be applied using, forexample, chemical vapor deposition (e.g. silanization), physical vapordeposition, electroplating, or sputtering. In other implementations, thesurface of any or all of the valve components can be coated with achemically inert material to prevent degradation of the valve due toprolonged exposure to the medium or to reduce reactivity with the fluid.Similarly, the surface of any or all of the valve components can becoated with an insulating layer to inhibit or prevent contact of thevalve materials with the fluid and prevent the release of toxic agentsfrom the components of the valve (e.g., if the fluid includes orinterfaces with a biological material).

In some implementations, the plurality of restrainers 122A-122D of thevalve can be fabricated using a deformable material. The deformation canbe passive, deforming as a function of the pressure applied on therestrainers 122A-122D by the disk 130 in the open state (secondposition). Alternative, the deformable material of the plurality ofrestrainers 122A-122D can be active, using any of the type of materialand actuation mechanisms described above. Deformation of the pluralityof restrainers 122A-122D can be used to, for example, increasemechanical resilience of the valve through passive bending of therestrainers 122A-122D under increased forward pressures or decrease theflow resistance of the valve under high forward pressures by increasingthe vertical spacing when the restrainers 122A-122D passively bend. Anactively deformable material can also be used to bias the position ofthe disk to the closed state (first position) or open state (secondposition), which would adjust the required forward or reserve pressureexerted by the fluid to induce transition between the open and theclosed states. Active actuation can be used to control the value of thetransition pressure.

EXEMPLARY APPLICATIONS

The valves (e.g., valve 100 and/or valve 200) described herein can beused in a variety of applications. For example, the valve 100 and/or thevalve 200 can be used with (e.g., connected in series with) any fluidicsystem or device to induce unidirectional flow within all or portion(s)of the system. The valve 100 and/or the valve 200 can induceunidirectional flow either passively through actuation of differences inpressure of the medium, or actively using any of the actuation materialsor methods described herein, to control the flow rate in portions(s) ofthe system (e.g. as a flow resistor) and to control the fluidcommunication between distinct portions (e.g., compartments) of thesystem.

In some implementations, the valve 100 and/or the valve 200 can be usedin flow chemistry applications to physically isolate the reactants andterminate a reaction in the flow chamber. A passive implementation ofthe valve 100 and/or the valve 200 can be used, using reverse pressureto seal the valve; or an active instance, using the external actuatingstimulus to seal the valve.

In some implementations, the valve 100 and/or the valve 200 can be usedas a passive or active valve when integrated in microfluidic roboticssystems to control the configuration and/or motion of the robot.

In some implementations, the valve 100 and/or the valve 200 can be usedfor generation of microfluidic droplets of arbitrary size and number ina multiphase system. In such implementations, the valve separates areservoir of the droplet medium and a reservoir of formed dropletswithin the encapsulating medium. A passive valve can be used to rectifythe flow of the droplet medium when the droplet medium reservoir isactuated by a periodic pressure or flow actuator. When the valve is inthe open state, the droplet medium is ejected through the valve forminga droplet, while when the valve enters the closed state, the droplet isformed and is released into the formed droplet reservoir. The flow rateand opening frequency of the valve are controlled to allow the dropletmedium to pass through the valve at the intended volume. With an activevalve, the valve is externally set to open and close at the desired flowrate and frequency using the actuating stimulus under potentiallyconstant cross-valve pressure.

In some implementations, the valves described herein can be used as avalve with a non-zero transition pressure. Any of the geometry alteringand actuation materials or techniques described above can be used toexert a controllable force on the disk and push it towards the closedstate (first position) or open state (second position). The controllableforce can be fixed or dynamically controlled by the actuation stimulusand can dictate the value of the non-zero transition pressure.

In some implementations, the valves described herein can be used as anultrasensitive flow-based pressure sensor. In such implementations, thevalve is placed between an externally controlled pressure and amicrofluidic system. If the valve opens and flow is detected, thecross-valve pressure in the system has exceeded the transition pressure.In a valve instance with active control over the transition pressure,the transition pressure value can be used to sweep the transitionpressure of the valve. The system would have minimal dead volumes, andits accuracy would depend on the accuracy of passive or active mechanismthat dictates the transition pressure of the valve.

In some implementations, the valves described herein can be used as anultrasensitive pressure/vacuum relief valve. In such implementations,the valve 100 and/or the valve 200 is placed at the output line of asystem whose pressure is within a predetermined range bounded by apredefined threshold. In such implementations, the valve is fabricatedwith a transition pressure matching the threshold of the system. If thesystem pressure crosses the predefined threshold, the valve opens,restoring the pressure to the desirable pressure range. An activelycontrolled valve can be used to dynamically regulate the predefinedthreshold and the pressure of the system.

In some implementations, the valves described herein can be used as animplantable valve (e.g. to substitute failing venous valves). The valvecan be placed as-is within blood vessels, or with structural additionson the outer side of a hollow body to improve adhesion and stabilitywithin the vessel. In such implementations, biocompatible materials areused to fabricate or coat the valve components.

In some implementations, the valves described herein can be used as avalvular component of generalized flow rectifier. The valve serves toinduce unidirectional flow when a cross-valve pressure actuation ofdynamic and arbitrary polarity is applied.

In some implementations, the valves described herein can be used withorgan-on-a-chip or other cell-containing technologies involving flow, tocontrol the flow rate of media and/or to rectify the flow profile toenable pulsatile flow. The flow can be externally induced (e.g. using apump or gravitational force), or it could be generated by contractingcells (skeletal muscle cells, smooth muscle cells, cardiomyocytes).

In some implementations, the valves described herein can be used as adrug switch in drug perfusion chambers, for example, in miniaturizedimplanted in-vivo drug delivery systems. The valve allows unidirectionalejection of the drug to the adjacent tissue/organ/circulation to preventcontamination of the drug stock. The valve resistance can be adjusted tominimize the ejected volume, allowing for higher drug concentrations andlonger lasting drug stock. The small size and compact nature of thevalve allows miniaturization of the system.

In some implementations, the valves described herein can be used as avalvular component of a wirelessly actuated system. The active valvematerial components described above can be used with a stimulusgenerator (e.g., electrical, optical, thermal, magnetic, etc.). Acoupled antenna within the system can be used for electrical, magneticand thermal actuation, an external light source can be used for opticalactuation, and external heat generators or heating light sources can beused for thermal actuation.

In some implementations, the valves described herein (e.g., valve 100)can be used within a fluid network having any suitable purpose andfunction, including organ-on-a-chip applications where the pumpcomprises one component of multiple components connected in series, eachcontaining a different type of tissue.

Cardiac Applications

One specific example of a micro-fluidic device that can be used with thevalves described herein is a micro-cardiac device, which can be used tostudy cardiac function. The micro-cardiac device can be used, forexample, to model the effect of hemodynamic load changes on cardiacfunction and the progression of ventricular cardiomyopathies as observedin vivo on a tissue, cellular and/or subcellular level. This modelingcan be used to study, for example, the myocardial response topathologically increased loading conditions, and how it correlates tochanges in cellular morphology, subcellular architecture, geneexpression and calcium handling. The micro-cardiac device acts as acyclic pulsatile pressure generator to produce pumping action causing aunidirectional flow.

Referring to FIG. 7, a microfluidic system includes a first valve 100A,a second valve 100B, and a micro-cardiac device 300. The micro-cardiacdevice 300 includes a heart tube chamber 310, a first well 320, and asecond well 330. A first channel portion 360A permits fluidcommunication between the first well 320 and the heart tube chamber 310and a second channel portion 360B permits fluid communication betweenthe heart tube chamber 310 and the second well 330. The heart tubechamber 310 includes cardiac tissue 312. The cardiac tissue 312 includescardiomyocytes (cardiac muscle cells), though other suitable cell types(e.g., endothelial cells, fibroblasts, pacemaker cells, perivascularcells) can also be included.

The cardiac tissue 312 can self-generate contractions to apply pressureon fluid within the micro-cardiac device 300 and induce fluid flow. Asshown in FIG. 7, the first valve 100A is positioned between the firstwell 320 and the heart tube chamber 310 and the second valve 100B ispositioned between the heart tube chamber 310 and the second port 330.The first valve 100A and the second valve 100B are the same as, orsimilar to, the valve 100 (FIGS. 1A-2D) described herein. Alternatively,the valve 100A and/or the valve 200 can be the same as, or similar to,the valve 200 (FIGS. 6A-6B) described herein.

The cardiac tissue 312 is isolated from the rest of the fluid networkthrough the first valve 100A and the second valve 100B. This allowsfluid to enter cavity of the cardiac tissue 312 in the direction ofarrow A from the first well 320 towards the cardiac tissue 312 throughthe first valve 100A during relaxation of the cardiac tissue 312, whileat the same time the second valve 100B inhibits flow from the secondport 330 and the cardiac tissue 312 in the direction opposite of arrowA. Conversely, during contraction of the cardiac tissue 312, the firstvalve 100A prevents fluid flow in the opposite direction of arrow A fromthe cardiac tissue 312 towards the first well 320, while the secondvalve 100B permits fluid flow in the direction of arrow A from thecardiac tissue 312 towards the second well 330. In other words, thefirst valve 100A and the second valve 100B cause unidirectional flowthrough the micro-cardiac device 300. While the microfluidic system inFIG. 7 is shown as including two valves (the first valve 100A and thesecond valve 100B), in other implementations, the microfluidic systemcan include any suitable number of valves that are the same as, orsimilar to, the first valve 100A and the second valve 100B (e.g., fourvalves).

Exemplary applications of the microfluidic system of FIG. 7 includemodeling cardiac physiology and pathology in response to variation ofblood pressure levels. In such applications, the liquid pressure in theinput port of the first well 320 (preload pressure) and the pressure inthe output port of the second well 30 (afterload pressure) can bedifferent (e.g., the afterload pressure is higher). In this case, thepressure within the cardiac tissue 312 can oscillate between the preloadand afterload pressures when the valves 100A and 100B rectify the fluidflow (e.g., the valves 100A and 100B open and close). This processmimics the function of the cardiac ventricles and their exposure to acyclic oscillating level of blood pressure. Varying the preload andafterload pressure can model the effect of blood pressure changes oncardiac function.

Other exemplary applications of the microfluidic system of FIG. 7includes use as a platform for drug screening regarding cardiotoxicity,where the pumping performance of the cardiac tissue 312 is used as oneof the metrics of cardiac health. Additionally, the microfluidic systemof FIG. 7 can be used as a platform for drug screening regarding theefficacy on pharmacological targets for cardiac disease, includinghypertrophic and dilated cardiomyopathy, arrhythmia, cardiacinflammation, fibrosis, recovery from ischemic shocks, or anycombination thereof. The system can also be used in organ-on-a-chipapplications.

All aforementioned exemplary applications can be used in conjunctionwith specific cell lines of cardiac tissue that are derived frompatients (e.g., either as primary cells or produced from inducedpluripotent stem cells) as a tool of “personalized medicine” to studythe behavior of the cardiac tissue of the specific patient.

Referring now to FIGS. 8A-8F, an exemplary process for fabricating themicro-cardiac device 300 is illustrated. As shown in FIG. 8A, thefabrication process begins with a rectangular shaped body 302 comprisinga material that is biocompatible with the heart tissue, such as, forexample, Polydimethylsiloxane (PDMS). As described above, themicro-cardiac device 300 includes the heart tube chamber 310, the firstwell 320, and the second well 330, which are in fluid communication withone another via channels within the body 302. While the micro-cardiacdevice 300 is shown as having two wells (first well 320 and second well330), in other implementations, the micro-cardiac device 300 can includeany suitable number of wells.

As shown in FIG. 8B, a first needle 340 is fit into the channels of thebody 302, such that the first needle 340A extends into the heart tubechamber 310. A gel that provides structure support for the cardiactissue (e.g., collagen) is inserted into the tube chamber 310 via thefirst needle 340A. After the gel is set (e.g., after gelation of thecollagen) the needle 340 is removed from the body 302, leaving a hollowchannel in the gel (e.g., collagen) in the heart tube chamber 310, asshown in FIG. 8B.

Next, as shown in FIG. 8D, a first needle guide 350A is inserted betweenthe first well 320 and the heart tube chamber 310 and a second needleguide 350B is inserted between the heart tube chamber 310 and the secondwell 330. In some implementations, the needle guides 350A and/or 350Bare fabricated using the same or similar methods as the valves describedherein (e.g., the valve 100 and/or the valve 200). A second needle 340Bis inserted into the channel of the body 302, crossing the heart tubechamber 310. The first and second needle guides 350A and 350B aid inguiding the second needle 340B through the channel made by the firstneedle 340A (FIG. 8B).

Thereafter, as shown in FIG. 8E, a mixture of cardiac cells, stromalcells and extracellular matrix (ECM) proteins (e.g., fibrin, collagen,Matrigel, other ECM proteins, or any combination thereof) is added tothe first well 320 and the body 302 is tilted so that the cellsprecipitate through the channel into the hollow space in the heart tubechamber 310. After the aforementioned mixture is added, the secondneedle 340B, the plugs 350A and 350B, and the remainder of the gelledmixture that is not contained within the heart tube chamber 310 areremoved, leaving behind a hollow channel in the heart tube chamber 310lined with cardiac tissue, as shown in FIG. 8F.

Referring generally to FIGS. 9A and 9B, an alternative microfluidicsystem 400 includes a concave cardiac tissue portion 410, a first port420, a second port 430, the first valve 100A, and the second valve 100B.The first valve 100A and the second valve 100B are the same as, orsimilar to, the first valve 100A and the second valve 100B,respectively, in FIG. 7. The first port 420 has an inlet 422 and thesecond port 430 has an outlet 432. The concave cardiac tissue portion410 is similar to the cardiac tissue 312 (FIG. 7) in that the concavecardiac tissue portion 410 can contract and relax to induce fluid flowthrough the system 400 and simulate cardiac function. In system 400,fluid enters through the inlet 422 of the first port 420 and exitsthrough the outlet 432 of the second port 420.

In some implementations, metamaterial scaffolds are used to modulate themechanical environment of living tissue. For example, the metamaterialis used as a mechanical stimulus to direct cellular growth, and tissuearchitecture. Accordingly, in another aspect provided herein is ascaffold composed of a metamaterial. The metamaterial scaffold comprisesa structure defining a lumen. The outer surface of the structurecomprises biological cells seeded thereon. For example, at least aportion of the outer surface, e.g., non-lumen surface of the structurecan comprise a layer of biological cells.

The design and functionality of the scaffold depend on the type of organor organ function one wishes to mimic. Thus, as noted above, themetamaterial scaffold can be of any shape or form that defines a lumen.For example, the structure defining a lumen can have a plain geometry.Some exemplary plain geometries include, but are not limited to tubular,sphere, hemisphere, bending tube and the like. The metamaterial scaffoldcan also be of geometry that resembles the native structure of a tissueor organ, e.g., a blood vessel. In some implementations, themetamaterial scaffold comprises a tubular structure defining first andseconds ends, and a lumen. In some implementations, the metamaterialscaffold is a tubular structure defining first and seconds ends, and thelumen. Generally, the first and second ends are open such that a fluidflow can occur through the tubular structure from the first end to thesecond end or vice versa. In some implementations, one of the first orsecond end is closed, i.e., a fluid flow does not occur through theclosed end.

As used herein, a “metamaterial” is an assembly of multiple individualelements. These elements are fashioned from conventional materials suchas metals or plastics, but the materials are usually arranged inspecific periodic patterns. Therefore, metamaterials gain theirproperties not only from their composition, but also from theirstructures. Metamaterials have properties that are not found in the bulkmaterials, which can include electromagnetic radiation, sound waves,electrical properties and mechanical properties. Mechanicalmetamaterials are metamaterials which have mechanical properties thatcan be designed to have properties not found in nature.

In some implementations, the metamaterials are made using additivemanufacturing methods. In some embodiments, the additive manufacturingmethod is TPDLW.

Exemplary mechanical metamaterials include “auxetic” materials, whichare materials that exhibit a Negative Poisson's Ratio. Therefore, whenan auxetic material is stretched by an applied force in a firstdirection, it becomes larger in a second direction perpendicular to thefirst direction. Alternatively, if an auxetic material is compressed byan applied force in the first direction, it becomes smaller in a seconddirection which is perpendicular to the first direction. The expansionin the second direction is not necessarily linearly related to expansionin the first direction due to the applied force, it is the generaldirection of expansion/contraction that defines an auxetic material.This is not a behavior that is generally found in nature wherecompression, for example, in one direction generally leads to anexpansion of the material in a second direction.

It is noted that references to auxetic material herein include materialswhich are intrinsically auxetic and materials which have been renderedauxetic. Further, the auxetic, material may be a synthetic auxeticmaterial and may have a macroscopic or microscopic auxetic structure.The auxetic material may be polymeric. The auxetic, material forming thescaffold may comprise a biodegradable polymer or polymers.

In some embodiments, scaffold uses a geometry of inverted hexagons inorder to effect auxetic properties in the metamaterial scaffold whichwould otherwise not be auxetic. These “inverted hexagons” are not“regular” hexagons and instead essentially comprise a hexagon havingfirst and second sides opposite and generally parallel to one another,and then third, fourth, fifth and sixth inwardly-inclined sides joiningthem. By linking chains of such inverted hexagons together via theirthird, fourth, fifth and/or sixth sides, then an auxetic structure canbe created. Obviously, it is possible to incorporate into suchstructures inverted hexagons which are linked together via the verticesof their first and second sides, although this may result in non-auxeticregions whilst still retaining the overall auxetic properties.

FIG. 12A illustrates an “inverted hexagon” unit cell for an exemplaryauxetic structure. FIG. 12B shows how the “inverted hexagon” unit cellscan be interconnected to form the auxetic structure (e.g., lattice ormesh). The FIGS. 12A and 12B show how expansion in the vertical andhorizontal direction are coupled. The dotted lines in FIG. 12B outlinethe expanded dimensions for the four-unit lattice and show how in thecontracted state, the lattice dimensions are reduced in both horizontaland vertical directions.

As shown in FIG. 12A, the inverted hexagon unit cell comprises a set ofsix points A, B, C, D, E, and F, which are interconnected by sixstraight or curved members as follows: a first member interconnectingpoints A and B; a second member interconnecting points B and C; a thirdmember interconnecting points C and D; a fourth member interconnectingpoints D and E; a fifth member interconnecting points E and F; and asixth member interconnecting points F and A. In some implementations,the connections are beams of rectangular cross-section with 4×4 um size,the angle of the inverted hexagon (angle ABC in FIG. 12A) is 35 degrees,length of the member interconnecting points B and C is 240 um long, andthe distance between points B and F in the relaxed state is 240 um

The unit cells of inverted hexagons form the auxetic structure shown inFIG. 12B by connection of each unit cell to adjacent ones forming a meshor 2D lattice. As shown, point D of a first unit cell is connected by amember (which can be curved or straight) to point A of an adjoining unitcell, a member BC of the first unit cell and member FE of adjoining unitcells are condensed forming a connection. Here “condensed” denotes thatthe two members become or form a single indistinguishable member and canrefer to a straight or curved member, or to a point or vertex.

In some implementations, a cylindrical metamaterial scaffold is made byconnection of rows where point D of a first unit cell is connected to anadjacent unit cell at point A until completing a band, forming a tubularstructure. In another embodiment, a metamaterial scaffold is made bycondensing of a member BC of a first unit cell with a member FE ofanother unit cell until completing a band and forming a structure.

FIGS. 12C and 12D illustrate another implementation of an auxeticstructure, a “rotating square” structure. Here the unit cell can bedescribed as comprising four squares as shown in FIG. 12C which areinterconnected at vertices to form the auxetic structure. FIGS. 12C and12D show how expansion in the vertical and horizontal direction arecoupled, where the individual squares rotate (e.g., about and axisperpendicular to the plane containing the squares) to provide theexpansion and contraction. The dotted lines in FIG. 12D outline theexpanded dimensions for the lattice and show how in the contractedstate, the lattice dimensions are reduced in both horizontal andvertical directions.

As shown in FIG. 12C, the rotating square unit cell can be describedfour squares with vertices which are labeled as G, H, I, J, K, L, M, N,O. P, Q and R, and which are interconnected by sixteen straight orcurved members as follows: a first member interconnecting points G andH; a second member interconnecting points H and I; a third memberinterconnecting points I and J; a fourth member interconnecting points Jand G; a fifth member interconnecting points J and K; a sixth memberinterconnecting points K and L; a seventh member interconnecting point Land M; an eight member interconnecting points M and J; a ninth memberinterconnecting points M and N; a tenth member interconnecting points Nand O; an eleventh member interconnecting points O and P; a twelfthmember interconnecting points P and M; a thirteenth memberinterconnecting points P and Q; a fourteenth member interconnectingpoints Q and R; a fifteenth member interconnecting points R and I; andsixteenth member interconnecting points I and P.

The rotating square unit cells form the auxetic structure shown in FIG.12D by connection of each unit cell to adjacent ones forming a mesh or2D lattice. As shown, in the horizontal direction, a point or vertices Lfrom a first unit cell is condensed with point H of an adjacent cell,and a point N of the first unit cell is condensed with point R of theadjacent unit cell. In the vertical direction, the point G of the firstunit cell is condensed with point Q of an adjacent unit cell, and thepoint K of the first unit cell is condensed with the point O of theadjacent unit cell.

In some implementations, a cylindrical metamaterial scaffold is made byconnection of rows where point L from a first unit cell is condensedwith point H of an adjacent cell, and a point N of the first unit cellis condensed with point R of the adjacent unit cell until completing aband, forming a tubular structure. In another embodiment, a cylindricalmetamaterial scaffold is made wherein the point G of the first unit cellis condensed with point Q of an adjacent unit cell, and the point K ofthe first unit cell is condensed with the point O of the adjacent unitcell until completing a band and forming a tubular structure.

FIGS. 12E and 12F show additional implementations of auxetic structures.FIG. 12E shows a “star” structure, in a compressed form on the left andexpanded form on the right. FIG. 12F shows a “rotating triangle”structure, compressed form on the left and expanded form on the right.The dashed lines indicate the approximate expanded dimensions and areadded to help guide the eyes and show the effect of expansion andcontraction. The rotating triangle unit cells form the auxetic structureshown in FIG. 12F by connection of each unit cell to adjacent onesforming a mesh or 2D lattice. As shown, each triangle unit cell isconnected to three other each triangle unit cells. Each vertex is sharedby two triangle unit cells.

In some implementations, the cylindrical metamaterial scaffold is madeby connecting the lattice shown in FIG. 12B, FIG. 12D, FIG. 12E or FIG.12F in directions other than the horizontal or vertical direction. Forexample, the lattice can form a band in a direction diagonal to thelattice or any angle between horizontal and vertical.

In some implementations, the auxetic structure of the scaffold comprisesa plurality of unit cells, each unit cell comprising a set of eightpoints interconnected with eight straight or curved members as follows:a first member interconnecting points A and B; a second memberinterconnecting points B and C; a third member interconnecting points Cand D; a fourth member interconnecting points C and E; a fifth memberinterconnecting points E and F; a sixth member interconnecting points Fand G; a seventh member interconnecting points G and H; and an eighthmember interconnecting points G and A. The unit cells form the auxeticstructure by connection of each unit cell to adjacent ones forming amesh or 2D lattice. For example, point D of first unit cell is connectedby a member (which can be curved or straight) to point H of an adjoiningunit cell and/or line AB of a first unit cell is condensed with EF of anadjoining cell.

To form the tubular structure, the unit cells are connected in rowsuntil completing a band and forming a tubular structure. For example,the unit cells are connected in rows with the point D of one cell beingconnected to point H of an adjoining cell until completing a band,thereby forming the tubular structure. In this example, the unit cellscan also be connected in columns along the length of the tubularstructure with the line AB of one cell being condensed to line EF of anadjoining cell until spanning the length of the tubular structure.

In another example, the unit cells are connected in rows with the lineAB of one cell being condensed to line EF of an adjoining cell untilcompleting a band, thereby forming the tubular structure. In thisexample, the unit cells can also be connected in columns along thelength of the tubular structure with the point D of one cell beingconnected to point H of an adjoining cell until spanning the length ofthe tubular structure.

In some implementations, the auxetic structure of the scaffold comprisesa plurality of unit cells, each unit cell comprising a set of fourpoints interconnected with four straight or curved members as follows: afirst member interconnecting points I and J; a second memberinterconnecting points J and K; a third member interconnecting points Kand L; and a fourth member interconnecting points L and I. The unitcells form the auxetic structure by connection of each unit cell toadjacent ones forming a mesh or 2D lattice. For example, point K offirst unit cell is condensed to point I of an adjoining unit cell and/orpoint L of first unit cell is condensed to point J of an adjoining unitcell.

To form the tubular structure, the unit cells are connected in rowsuntil completing a band and forming a tubular structure. For example,the unit cells are connected in rows with the point K of one cell beingcondensed to point I of an adjoining cell until completing a band andthereby forming the tubular structure. In this example, the unit cellscan also be connected in columns along the length of the tubularstructure with the point L of one cell being condensed to point J of anadjoining cell until spanning the length of the tubular structure.

In another example, the unit cells are connected in rows with the pointL of one cell being condensed to point J of an adjoining cell untilcompleting a band and thereby forming the tubular structure. In thisexample, the unit cells can also be connected in columns along thelength of the tubular structure with the point K of one cell beingcondensed to point I of an adjoining cell until spanning the length ofthe tubular structure.

In some implementations, the auxetic structure of the scaffold of thepresent invention comprises a plurality of unit cells, each unit cellcomprising a set of twelve points interconnected with twelve straight orcurved members as follows: a first member interconnecting points A andB; a second member interconnecting points B and C; a third memberinterconnecting points B and D; a fourth member interconnecting points Dand E; a fifth member interconnecting points E and F; a sixth memberinterconnecting points E and G; a seventh member interconnecting pointsG and H; an eighth member interconnecting points H and I; a ninth memberinterconnecting points H and J; a tenth member interconnecting points Jand K; an eleventh member interconnecting points K and L; and a twelfthmember interconnecting points K and A. The unit cells form the auxeticstructure by connection of each unit cell to adjacent ones forming amesh or 2D lattice. For example, point F of first unit cell is connectedto point L of an adjoining unit cell and/or point C of first unit cellis connected to point I of an adjoining unit cell

To form the tubular structure, the unit cells are connected in rows withthe point F of one cell being connected to point L of an adjoining celluntil completing a band and thereby forming the tubular structure. Inthis example; the unit cells can also be connected in columns along thelength of the tubular structure with the point L of one cell beingconnected to point F of an adjoining cell until spanning the length ofthe tubular structure.

Alternatively, the unit cells are connected in rows with the point C ofone cell being connected to point I of an adjoining cell untilcompleting a band and thereby forming the tubular structure. In thisexample, the unit cells can also be connected in columns along thelength of the tubular structure with the point C of one cell beingconnected to point I of an adjoining cell until spanning the length ofthe tubular structure.

While the above describe the case where the band of unit cells isvertical to the axial direction of the tubular structure by repeatingthe unit cell along the cell's horizontal or vertical direction, it isnoted a cylindrical metamaterial scaffold can also be made by connectingthe lattices and unit cells shown in FIGS. 12A-12F or described hereinin directions other than the horizontal or vertical direction. Forexample, the unit cells can be connected to form a band in a directiondiagonal to the lattice or any angle between horizontal and vertical.

The figures and descriptions of particular auxetic structures should notbe construed as limiting embodiments since there are many known auxeticstructures that can be implemented for the metamaterial scaffoldsdescribed herein. To allow for auxetic behavior, any other auxetic unitcell and structure can be used (Karnesis et al. Small Materials andStructures, 2013). In addition to two dimensional structures, the unitcells can be three dimensional. In some embodiments the combination ofunit cells provides behaviors that include torsion uponcompression/tension, in inhomogeneous anisotropy stiffness and can, forexample, control bending when a particular force is applied. As usedherein a lumen is the inside space of a tubular structure. In someembodiments, the lumen of the cylindrical metamaterial scaffold does notinclude any biological cells.

In some implementations, the lumen of the scaffold also comprisesbiological cells. In such implementations, the amount of biologicalcells in the lumen can be less than the amount of biological cells onthe outer or non-lumen surface

A skilled artisan can implant various types of cells, i.e., biologicalcells on the scaffold. Cells include any cell type from a multicellularstructure, including nematodes, amoebas, up to mammals such as humans.Generally, cell types implanted on the scaffold depend on the type oforgan or organ function one wishes to mimic, and the tissues thatcomprise those organs. It is noted that cells can be of single cell-typeor mixture or co-culture of different types. One can also co-culturevarious stem cells, such as bone marrow cells, induced adult stem cells,embryonal stem cells or stem cells isolated from adult tissues on thescaffold of the invention. Exemplary cell types (e.g., human) which canbe used include, but are not limited to cells of the integumentarysystem including but not limited to Keratinizing epithelial cells,Epidermal keratinocyte (differentiating epidermal cell), Epidermal basalcell (stem cell), Keratinocyte of fingernails and toenails, Nail bedbasal cell (stem cell), Medullary hair shaft cell, Cortical hair shaftcell, Cuticular hair shaft cell, Cuticular hair root sheath cell, Hairroot sheath cell of Huxley's layer, Hair root sheath cell of Henle'slayer, External hair root sheath cell, Hair matrix cell (stem cell); Wetstratified barrier epithelial cells, such as Surface epithelial cell ofstratified squamous epithelium of cornea, tongue, oral cavity,esophagus, anal canal, distal urethra and vagina, basal cell (stem cell)of epithelia of cornea, tongue, oral cavity, esophagus, anal canal,distal urethra and vagina, Urinary epithelium cell (lining urinarybladder and urinary ducts); Exocrine secretory epithelial cells, such asSalivary gland mucous cell (polysaccharide-rich secretion). Salivarygland serous cell (glycoprotein enzyme-rich secretion), Von Ebner'sgland cell in tongue (washes taste buds), Mammary gland cell (milksecretion), Lacrimal gland cell (tear secretion), Ceruminous gland cellin ear (wax secretion), Eccrine sweat gland dark cell (glycoproteinsecretion), Eccrine sweat gland clear cell (small molecule secretion),Apocrine sweat gland cell (odoriferous secretion, sex-hormonesensitive), Gland of Moll cell in eyelid (specialized sweat gland),Sebaceous gland cell (lipid-rich sebum secretion), Bowman's gland cellin nose (washes olfactory epithelium), Brunner's gland cell in duodenum(enzymes and alkaline mucus), Seminal vesicle cell (secretes seminalfluid components, including fructose for swimming sperm), Prostate glandcell (secretes seminal fluid components), Bulbourethral gland cell(mucus secretion), Bartholin's gland cell (vaginal lubricant secretion),Gland of Littre cell (mucus secretion), Uterus endometrium cell(carbohydrate secretion), Isolated goblet cell of respiratory anddigestive tracts (mucus secretion), Stomach lining mucous cell (mucussecretion), Gastric gland zymogenic cell (pepsinogen secretion), Gastricgland oxyntic cell (hydrochloric acid secretion), Pancreatic acinar cell(bicarbonate and digestive enzyme secretion), pancreatic endocrinecells, Paneth cell of small intestine (lysozyme secretion), intestinalepithelial cells, Types I and II pneumocytes of lung (surfactantsecretion), Clara cell of lung; hormone secreting cells, such asendocrine cells of the islet of Langerhands of the pancreas; Anteriorpituitary cells, Somatotropes, Lactotropes, Thyrotropes, Gonadotropes,Corticotropes, Intermediate pituitary cell, secretingmelanocyte-stimulating hormone; and Magnocellular neurosecretory cellssecreting oxytocin or vasopressin; Gut and respiratory tract cellssecreting serotonin, endorphin, somatostatin, gastrin, secretin,cholecystokinin, insulin, glucagon, bombesin; Thyroid gland cells suchas thyroid epithelial cell, parafollicular cell, Parathyroid glandcells, Parathyroid chief cell, Oxyphil cell, Adrenal gland cells,chromaffin cells secreting steroid hormones (mineralcorticoids and glucocorticoids), Leydig cell of testes secreting testosterone, Theca interimcell of ovarian follicle secreting estrogen, Corpus luteum cell ofruptured ovarian follicle secreting progesterone, Granulosa luteincells, Theca lutein cells, Juxtaglomerular cell (renin secretion),Macula densa cell of kidney, Peripolar cell of kidney, Mesangial cell ofkidney; Metabolism and storage cells such as Hepatocyte (liver cell),White fat cell, Brown fat cell, Liver lipocyte. One can also use Barrierfunction cells (Lung, Gut, Exocrine Glands and Urogenital Tract) orKidney cells such as Kidney glomerulus parietal cell, Kidney glomeruluspodocyte, Kidney proximal tubule brush border cell, Loop of Henle thinsegment cell, Kidney distal tubule cell, Kidney collecting duct cell;Type I pneumocyte (lining air space of lung), Pancreatic duct cell(centroacinar cell), Nonstriated duct cell (of sweat gland, salivarygland, mammary gland, etc.), principal cell, Intercalated cell, Ductcell (of seminal vesicle, prostate gland, etc.), Intestinal brush bordercell (with microvilli), Exocrine gland striated duct cell, Gall bladderepithelial cell, Ductulus efferens nonciliated cell, Epididymalprincipal cell, Epididymal basal cell; Epithelial cells lining closedinternal body cavities such as Blood vessel and lymphatic vascularendothelial fenestrated cell, Blood vessel and lymphatic vascularendothelial continuous cell, Blood vessel and lymphatic vascularendothelial splenic cell. Synovial cell (lining joint cavities,hyaluronic acid secretion), Serosal cell (lining peritoneal, pleural,and pericardial cavities), Squamous cell (lining perilymphatic space ofear), Squamous cell (lining endolymphatic space of ear), Columnar cellof endolymphatic sac with microvilli endolymphatic space of ear),Columnar cell of endolymphatic sac without microvilli endolymphaticspace of ear), Dark cell (lining endolymphatic space of ear), Vestibularmembrane cell (lining endolymphatic space of ear), Stria vascularisbasal cell (lining endolymphatic space of ear), Stria vascular ismarginal cell (lining endolymphatic space of ear), Cell of Claudius(lining endolymphatic space of ear), Cell of Boettcher (liningendolymphatic space of ear), Choroid plexus cell (cerebrospinal fluidsecretion), Pia-arachnoid squamous cell, Pigmented ciliary epitheliumcell of eye, Nonpigmented epithelium cell of eye, Corneal endothelialcell; Ciliated cells with propulsive function such as Respiratory tractciliated cell, Oviduct ciliated cell (in female), Uterine endometrialciliated cell (in female), Rete testis ciliated cell (in male), Ductulusefferens ciliated cell (in male), Ciliated ependymal cell of centralnervous system (lining brain cavities); cells that secrete specializedECMs, such as Ameloblast epithelial cell (tooth enamel secretion),Planum semilunatum epithelial cell of vestibular apparatus of ear(proteoglycan secretion), Organ of Corti interdental epithelial cell(secreting tectorial membrane covering hair cells). Loose connectivetissue fibroblasts, Corneal fibroblasts (corneal keratocytes), Tendonfibroblasts, Bone marrow reticular tissue fibroblasts. Othernonepithelial fibroblasts, Pericyte, Nucleus pulposus cell ofintervertebral disc, Cementoblast/cementocyte (tooth root bonelikecementum secretion), Odontoblast/odontocyte (tooth dentin secretion),Hyaline cartilage chondrocyte, Fibrocartilage chondrocyte, Elasticcartilage chondrocyte, Osteoblast/osteocyte, Osteoprogenitor cell (stemcell of osteoblasts), Hyalocyte of vitreous body of eye, Stellate cellof perilymphatic space of ear, Hepatic stellate cell (Ito cell),Pancreatic stellate cell; contractile cells, such as Skeletal musclecells, Red skeletal muscle cell (slow), White skeletal muscle cell(fast); Intermediate skeletal muscle cell, nuclear bag cell of musclespindle, nuclear chain cell of muscle spindle, Satellite cell (stemcell), Heart muscle cells; Ordinary heart muscle cell, Nodal heartmuscle cell, Purkinje fiber cell, Smooth muscle cell (various types),Myoepithelial cell of iris, Myoepithelial cell of exocrine glands; Bloodand immune system cells, such as Erythrocyte (red blood cell),Megakaryocyte (platelet precursor), Monocyte, Connective tissuemacrophage (various types); Epidermal Langerhans cell, Osteoclast (inhone), Dendritic cell (in lymphoid tissues), Microglial cell (in centralnervous system), Neutrophil granulocyte, Eosinophil granulocyte,Basophil granulocyte, Mast cell, Helper T cell, Suppressor T cell,Cytotoxic T cell, Natural Killer T cell, B cell, Natural killer cell.Reticulocyte, Stem cells and committed progenitors for the blood andimmune system (various types); Nervous system cells, Sensory transducercells such as Auditory inner hair cell of organ of Corti, Auditory outerhair cell of organ of Corti, Basal cell of olfactory epithelium (stemcell for olfactory neurons), Cold-sensitive primary sensory neurons,Heat-sensitive primary sensory neurons, Merkel cell of epidermis (touchsensor), Olfactory receptor neuron, Pain-sensitive primary sensoryneurons (various types); Photoreceptor cells of retina in eye includingPhotoreceptor rod cells, Photoreceptor blue-sensitive cone cell of eye,Photoreceptor green-sensitive cone cell of eye, Photoreceptorred-sensitive cone cell of eye, Proprioceptive primary sensory neurons(various types); Touch-sensitive primary sensory neurons (varioustypes); Type I carotid body cell (blood pH sensor); H carotid body cell(blood pH sensor); Type I hair cell of vestibular apparatus of ear(acceleration and gravity); Type II hair cell of vestibular apparatus ofear (acceleration and gravity); Type I taste bud cell; Autonomic neuroncells such as Cholinergic neural cell (various types), Adrenergic neuralcell (various types), Peptidergic neural cell (various types) in thepresent device. Further, sense organ and peripheral neuron supportingcells can also be used. These include, for example, inner pillar cell oforgan of Corti, Outer pillar cell of organ of Corti, Inner phalangealcell of organ of Corti, Outer phalangeal cell of organ of Corti, Bordercell of organ of Corti, Hensen cell of organ of Corti, Vestibularapparatus supporting cell, Type I taste bud supporting cell, Olfactoryepithelium supporting cell, Schwann cell, Satellite cell (encapsulatingperipheral nerve cell bodies) and/or Enteric glial cell. In someembodiments, one can also use central nervous system neurons and glialcells such as Astrocyte (various types), Neuron cells (large variety oftypes, still poorly classified), Oligodendrocyte, Spindle neuron;Anterior lens epithelial cell and Crystallin-containing lens fiber cell;pigment cells such as melanocytes and retinal pigmented epithelialcells; and germ cells, such as Oogonium/Oocyte, Spermatid, Spermatocyte,Spermatogonium cell (stem cell for spermatocyte), and Spermatozoon;membrane nurse cells such as Ovarian follicle cell, Sertoli cell (intestis), Thymus epithelial cell; and interstitial cells such asinterstitial kidney cells.

In some implementations, cells that are seeded onto the metamaterialscaffold are selected from the group consisting of cardiac, bone,skeletal muscle, smooth muscle, pulmonary (e.g., for simulating thealveoli and their expansion), esophageal and stomachal (e.g., simulatingthe smooth muscle contraction), intestinal (simulating the peristalticcontraction and the geometrical complexity of the villi) and vascularcells (simulating the lumen shape, its contraction and constrictionduring vasoconstriction and vasodilation, and its stretch underpulsatile blood pressure). In some embodiments cells that are supportedby or grown onto the metamaterial scaffold are cardiomyocytes.

In some implementations, the metamaterial scaffold can be made hollow,e.g., with pores on the surface, for example, to mimic the vascularsystem. The hollow network within the scaffold can be connected to adifferent series of channels and such hollow metamaterial scaffolds canbe used for perfusing the scaffold and the tissue with any medium (e.g.as a way of vascularization or drug perfusion). A homogeneous perfusioncan prevent necrosis of tissue due to poor nutrient diffusion, makingthicker tissues viable.

In some implementations, the lumen has a diameter between about 0.005 mmand about 50 mm, a diameter that is less than about 5 mm, a diameterthat is less than about 1 mm, a diameter that is less than about 0.1 mmor a diameter that is less than about 0.01 mm. In some implementations,the lumen has a diameter between about 0.008 mm and about 25 mm. In someimplementations, the lumen has a diameter of about 1 mm. In someimplementations, a length of the lumen is about 1.2 mm.

The scaffolds described herein can be fabricated from a biocompatiblematerial. As used herein, the term “biocompatible material” refers toany polymeric material that does not induce a significant immuneresponse or deleterious tissue reaction, e.g., toxic reaction orsignificant irritation, over time when implanted into or placed adjacentto the biological tissue of a subject, or induce blood clotting orcoagulation when it comes in contact with blood. Suitable biocompatiblematerials include derivatives and copolymers of a polyimides,poly(ethylene glycol), polyvinyl alcohol, polyethyleneimine, andpolyvinylamine, polyacrylates, polyamides, polyesters, polycarbonates,and polystyrenes.

In some implementations, the scaffold can be fabricated from a materialselected from the group consisting of polydimethylsiloxane, polyimide,polyethylene terephthalate, polymethylmethacrylate, polyurethane,polyvinylchloride, polystyrene polysulfone, polycarbonate,polymethylpentene, polypropylene, a poly dine fluoride, polysilicon,polytetrafluoroethylene, polysulfone, acrylonitrile butadiene styrene,polyacrylonitrile, polybutadiene, poly(butylene terephthalate),poly(ether sulfone), poly(ether ether ketones), poly(ethylene glycol),styrene-acrylonitrile resin, poly(trimethylene terephthalate), polyvinylbutyral, polyvinylidenedifluoride, poly(vinyl pyrrolidone), and anycombination thereof.

In some implementations, the scaffolds described herein can befabricated from a degradable material, for example, for the purpose ofinitially directing tissue growth until the tissue generates its ownsufficient extracellular matrix to stabilize its structure (e.g.,osteogenic tissue). Degradability can be achieved either by using amaterial that can be degraded by the cells, or where degradation isexternally induced by adding a soluble component that destabilizes thematerial's structure.

The scaffolds described herein can generally be manufactured orfabricated using any suitable technique or method, such as, for example,photolithography, two-photon laser lithography, stereolithography,reactive ion etching, or using molding where the mold is fabricatedusing any appropriate technique, including the aforementioned.

The material of the scaffold can be varied depending on the applicationand printing technique. In some implementations, the surface propertiesand chemistry of the scaffold are varied, either uniformly (e.g. plasmaetching, chemical vapor deposition, and silanization) or selectively atdesired locations on the scaffold. Selective modification can beachieved, for example, by using TPDLW to append a second photoresist ontop of the initial resist with different properties. Through selectiveapplication of the second resist, it is possible to control the affinityof cells on the scaffold and create patterns of adhesion sites on thescaffold (Richter et al. Advanced Materials, 2017). In someimplementations, the chemical properties of the surface are modifiedthrough passivation/activation, thus changing the affinity of othersubstances on the surface (e.g., for metal deposition and fluorescentlabeling—Ceylan et al. Advanced Materials, 2017). In someimplementations, an electrically conductive material can be used toprint the scaffold or to pattern the printed scaffold. Thus, in someimplementations, electrodes are included in or on the scaffold, that canbe used for electrical stimulation and/or recording.

Any suitable method can be used for seeding cells on the scaffold. Forexample, a needle can be inserted in the lumen and the scaffoldincubated in a culture of appropriate cells. After sufficient period oftime to allow the cells to adhere on the scaffold, the needle can beremoved from the lumen,

Also provided herein is a microfluidic device comprising a cylindricalscaffold described herein and a valve described herein in fluidcommunication with each other.

Referring to FIG. 13, an exemplary microfluidic device 1300 includes afirst valve 100A, a second valve 100B, a cylindrical scaffold 1310, afirst port 1320, and a second port 1330. A first channel portion 1360Apermits fluid communication between the first port 1320 and thecylindrical scaffold 1310 and a second channel portion 1360B permitsfluid communication between the cylindrical scaffold 1310 and the secondport 1330. In some embodiments, the cylindrical scaffold 1310 includescardiomyocytes and, optionally, other suitable cell types, such asendothelial cells, fibroblasts, pacemaker cells, and/or perivascularcells.

The cylindrical scaffold 1310 can self-generate contractions to applypressure on fluid within the microfluidic device 1300 and induce fluidflow. As shown in FIG. 13, the first valve 100A is positioned betweenthe first port 1320 and the cylindrical scaffold 1310 and the secondvalve 100B is positioned between the cylindrical scaffold 1310 and thesecond port 1330. The first valve 100A and the second valve 100B are thesame as, or similar to, the valve 100 (FIGS. 1A-2D) described herein.Alternatively, the valve 100A and/or the valve 200 can be the same as,or similar to, the valve 200 (FIGS. 6A-6B) described herein.

The cylindrical scaffold 1310 is isolated from the rest of the fluidnetwork through the first valve 100A and the second valve 100B. Thisallows fluid to enter lumen of the cylindrical scaffold 1310 in thedirection of arrow A through the first valve 100A and the first port1320 during relaxation of the cardiomyocytes seeded on the cylindricalscaffold 1310, while at the same time the second valve 100B inhibitsflow from the second port 1330 towards the cylindrical scaffold 1310 inthe opposite direction of arrow A. Conversely, during contraction of thecardiomyocytes seeded on the cylindrical scaffold 1310, the first valve100A prevents fluid flow in the opposite direction of arrow A towardsthe first port 1320, while the second valve 100B permits fluid flow inthe direction of arrow A from cylindrical scaffold 1310 towards thesecond port 1330. In other words, the first valve 100A and the secondvalve 100B cause unidirectional flow through the micro-cardiac device1300. While the microfluidic device in FIG. 13 is shown as including twovalves (the first valve 100A and the second valve 100B), in otherimplementations, the microfluidic device can include any suitable numberof valves that are the same as, or similar to, the first valve 100A andthe second valve 100B (e.g., four valves).

Referring generally to FIG. 14, another exemplary microfluidic device1400 includes a first valve 100A, a second valve 100B, a first port1420, a second port 1430, and a cylindrical scaffold 1410. A firstchannel portion 1460A permits fluid communication between the first port1420 and the cylindrical scaffold 1410 via a second channel portion1460C. A third channel portion 1460B permits fluid communication betweenthe second port 1430 and the cylindrical scaffold 1410 via the secondchannel portion 1460C. In some embodiments, the cylindrical scaffold1410 includes cardiomyocytes and, optionally, other suitable cell types,such as endothelial cells, fibroblasts, pacemaker cells, and/orperivascular cells.

The cylindrical scaffold 1410 can self-generate contractions to applypressure on fluid within the micro-cardiac device 1400, induce fluidflow and simulate cardiac function. In system 1400, fluid enters throughthe first port 1420 and exits through the second port 1430, or viceversa.

While the present disclosure has been described with reference to one ormore particular embodiments or implementations, those skilled in the artwill recognize that many changes may be made thereto without departingfrom the spirit and scope of the present disclosure. Each of theseimplementations and obvious variations thereof is contemplated asfalling within the spirit and scope of the present disclosure. It isalso contemplated that additional implementations according to aspectsof the present disclosure may combine any number of features from any ofthe implementations described herein.

ALTERNATIVE IMPLEMENTATIONS

Implementation 1.

A valve comprises a body including an inner bore extending between afirst port and a second port, a seat, and one or more restrainers, and adisk that is moveable between the seat and the one or more restrainerssuch that (i) a first pressure that is less than 1 pascal and applied ina first direction causes the disk to move from a first position towardsa second position to permit fluid communication between the first portand the second port and (ii) a second pressure that is less than 1pascal and applied in a second opposing direction causes the disk tomove from the second position towards the first position to inhibitfluid communication between the first port and the second port.

Implementation 2.

The valve according to implementation 1, wherein the first pressure andthe second pressure are less than 0.5 pascals.

Implementation 3.

The valve according to implementations 1 or 2, wherein the firstpressure is between about 0.1 pascals and about 0.5 pascals.

Implementation 4.

The valve according to any one of implementations 1-3, wherein thesecond pressure is between about 0.05 pascals and about 0.2 pascals.

Implementation 5.

The valve according to any one of implementations 1-4, wherein the diskis moveable such that the first pressure causes the disk to move fromthe first position to the second position in less than 500 milliseconds.

Implementation 6.

The valve according to any one of implementations 1-5, wherein the bodyis cylindrical and has a first diameter is that is 400 microns or lessand a longitudinal length that is 1110 microns or less, and the innerbore is cylindrical and has a second diameter that is 300 microns orless.

Implementation 7.

The valve according to any one of implementations 1-6, wherein adistance between the disk and the one or more restrainers is betweenabout 10 microns and about 30 microns responsive to the disk being inthe second position.

Implementation 8.

The valve according to any one of implementations 1-7, wherein the bodyis rigid.

Implementation 9.

The valve according to any one of implementations 1-8, wherein the bodyis monolithic.

Implementation 10.

The valve according to any one of implementations 1-9, wherein the diskincludes a cylindrical portion and a spherical portion, wherein aportion of the spherical portion contacts the seat responsive to thedisk being in the first position to aid inhibiting fluid communicationbetween the first port and the second port.

Implementation 11.

The valve according to any one of implementations 1-10, wherein thespherical portion of the disk has a degree of curvature that is betweenabout 30 degrees and about 60 degrees.

Implementation 12.

The valve according to any one of implementations 1-11, wherein adistance between the first port and the seat is between about 5% andabout 15% of a longitudinal length of the body.

Implementation 13.

A valve for use in a microfluidic system, the valve comprising a bodyincluding an inner bore extending between a first port and a secondport, a seat having an opening and being disposed within the inner bore,and a plurality of restrainers positioned between the seat and thesecond port, and a disk that is moveable relative to the seat and theplurality of restrainers such that application of a first predeterminedpressure that is between about 0.05 pascals and 1 pascal causes the diskto move from a first position towards a second position to permit fluidcommunication between the first port and the second port.

Implementation 14.

The valve according to implementation 13, wherein the disk inhibitsfluid communication between the first port and the second portresponsive to being in the first position.

Implementation 15.

The valve according to implementation 14, wherein a spherical portion ofthe disk is partially disposed within the opening of the seat to aid ininhibiting fluid communication between the first port and the secondport responsive to the disk being in the first position.

Implementation 16.

The valve according to implementations 14 or 15, wherein the disk ismoveable such that application of a second predetermined pressure causesthe disk to move from the second position towards the first position toinhibit fluid communication between the first port and the second port.

Implementation 17.

The valve according to implementation 16, wherein the firstpredetermined pressure is different than the second predeterminedpressure.

Implementation 18.

The valve according to any of implementations 13-17, wherein the diskincludes a spherical portion and a cylindrical portion having a firstdiameter that is less than a second diameter of the inner bore.

Implementation 19.

The valve according to implementation 18, wherein a third diameter ofthe opening of the seat is equal to or smaller than twice the firstdiameter minus the second diameter.

Implementation 20.

The valve according to any one of implementations 13-19, wherein thebody is monolithic.

Implementation 21.

A micro-fluidic system comprising a micro-cardiac device including aheart tube chamber containing cardiac cells, a first port, a secondport, the heart tube chamber, the first port, and the second port, thefirst port being in fluid communication with the heart tube chamber viaa first channel portion, the second port being in fluid communicationwith the heart tube chamber via a second channel portion; a first valvedisposed in the first channel portion; and a second valve disposed inthe second channel portion, wherein the first valve and the second valveare configured to cause unidirectional flow through the heart tubechamber.

Implementation 22.

A method for making a micro-cardiac device, the method comprising:inserting a first needle of a first diameter into a channel of a bodysuch that the first need extends into a heart tube chamber disposedwithin the body; injecting a gel into the heart tube chamber via thefirst needle; removing the first needle subsequent to setting of thegel; inserting a first needle guide between a first well and the hearttube chamber; inserting a second needle guide between the heart tubechamber and a second well; inserting a second needle of a seconddiameter smaller than the first diameter into the channel such that thesecond needle extends into the heart tube chamber; injecting cells intothe heart tube chamber; and removing the second needle.

Implementation 23.

The method according to claim 22, wherein the cells include cardiaccells, stromal cells, extracellular matrix (ECM) proteins, fibrin,collagen, Matrigel, or any combination thereof

Implementation 24.

The method according to claim 22 or 23, wherein the gel is collagen,fibrin, Matrigel, a synthetic hydrogel, or any combination thereof.

Implementation 25.

The method according to any one of claims 22-24, wherein the bodycomprises polydimethylsiloxane (PDMS).

Implementation 26.

A metamaterial scaffold, comprising: (i) a structure defining a lumen;(ii) at least a portion of an outer or non-lumen surface of the tubularstructure is coated with a plurality of biological cells, and whereinthe structure is composed of a metamaterial.

Implementation 27.

The metamaterial scaffold according to implementation 26, wherein thestructure is of a plain geometric shape.

Implementation 28.

The metamaterial scaffold according to implementation 26, wherein thestructure has a shape of a native structure of a tissue.

Implementation 29.

The metamaterial scaffold according to any one of implementations 26-28,wherein the structure is a tubular structure defining first and secondends, and the lumen.

Implementation 30.

The metamaterial scaffold according to any one of implementations 26-29,wherein the structure is composed of an auxetic material.

Implementation 31.

The metamaterial scaffold according to any one of implementations 26-31,wherein the metamaterial comprises an auxetic structure.

Implementation 32.

The metamaterial scaffold of implementation 31, wherein the auxeticstructure comprises a plurality of unit cells, each unit cell comprisinga set of six points interconnected with six straight or curved members,including: a first member interconnecting points A and B; a secondmember interconnecting points B and C; a third member interconnectingpoints C and D; a fourth member interconnecting points D and E; a fifthmember interconnecting points E and F; and a sixth memberinterconnecting points F and A.

Implementation 33.

The metamaterial scaffold of implementation 32, wherein the unit cellsare connected in rows with the point D of one cell being connected topoint A of an adjoining cell until completing a band around the tubularstructure.

Implementation 34.

The metamaterial scaffold according to implementation 32 or 33, whereinthe unit cells are connected in columns along the length of thestructure with the line AB of one cell being connected to line EF of anadjoining cell until spanning the length of the structure.

Implementation 35.

The auxetic scaffold of implementation 31, wherein the unit cells areinverted hexagon unit cells.

Implementation 36.

The metamaterial scaffold according to any one of implementations 26-35,wherein the plurality of biological cells comprises a cell selected fromthe exemplary group consisting of cardiac muscle, bone, skeletal muscle,smooth muscle, pulmonary, esophageal and stomachal, intestinal cells,vascular cells, keratinizing epithelial cells, Epidermal keratinocyte(differentiating epidermal cell), Epidermal basal cell (stem cell),Keratinocyte of fingernails and toenails, Nail bed basal cell (stemcell), Medullary hair shaft cell, Cortical hair shaft cell, Cuticularhair shaft cell, Cuticular hair root sheath cell, Hair root sheath cellof Huxley's layer, Hair root sheath cell of Henle's layer, External hairroot sheath cell, Hair matrix cell (stem cell); Wet stratified barrierepithelial cells, such as Surface epithelial cell of stratified squamousepithelium of cornea, tongue, oral cavity, esophagus, anal canal, distalurethra and vagina, basal cell (stem cell) of epithelia of cornea,tongue, oral cavity, esophagus, anal canal, distal urethra and vagina,Urinary epithelium cell (lining urinary bladder and urinary ducts);Exocrine secretory epithelial cells, such as Salivary gland mucous cell(polysaccharide-rich secretion), Salivary gland serous cell(glycoprotein enzyme-rich secretion), Von Ebner's gland cell in tongue(washes taste buds), Mammary gland cell (milk secretion), Lacrimal glandcell (tear secretion), Ceruminous gland cell in ear (wax secretion),Eccrine sweat gland dark cell (glycoprotein secretion), Eccrine sweatgland clear cell (small molecule secretion), Apocrine sweat gland cell(odoriferous secretion, sex-hormone sensitive), Gland of Moll cell ineyelid (specialized sweat gland), Sebaceous gland cell (lipid-rich sebumsecretion), Bowman's gland cell in nose (washes olfactory epithelium),Brunner's gland cell in duodenum (enzymes and alkaline mucus), Seminalvesicle cell (secretes seminal fluid components, including fructose forswimming sperm), Prostate gland cell (secretes seminal fluidcomponents), Bulbourethral gland cell (mucus secretion), Bartholin'sgland cell (vaginal lubricant secretion), Gland of Littre cell (mucussecretion), Uterus endometrium cell (carbohydrate secretion), Isolatedgoblet cell of respiratory and digestive tracts (mucus secretion),Stomach lining mucous cell (mucus secretion), Gastric gland zymogeniccell (pepsinogen secretion), Gastric gland oxyntic cell (hydrochloricacid secretion), Pancreatic acinar cell (bicarbonate and digestiveenzyme secretion), pancreatic endocrine cells, Paneth cell of smallintestine (lysozyme secretion), intestinal epithelial cells, Types I andII pneumocytes of lung (surfactant secretion), Clara cell of lung;hormone secreting cells, such as endocrine cells of the islet ofLangerhands of the pancreas, Anterior pituitary cells, Somatotropes,Lactotropes, Thyrotropes, Gonadotropes, Corticotropes, Intermediatepituitary cell, secreting melanocyte-stimulating hormone; andMagnocellular neurosecretory cells secreting oxytocin or vasopressin;Gut and respiratory tract cells secreting serotonin, endorphin,somatostatin, gastrin, secretin, cholecystokinin, insulin, glucagon,bombesin; Thyroid gland cells such as thyroid epithelial cell,parafollicular cell, Parathyroid gland cells, Parathyroid chief cell,Oxyphil cell, Adrenal gland cells, chromaffin cells secreting steroidhormones (mineralcorticoids and gluco corticoids), Leydig cell of testessecreting testosterone, Theca internal cell of ovarian folliclesecreting estrogen, Corpus luteum cell of ruptured ovarian folliclesecreting progesterone, Granulosa lutein cells, Theca lutein cells,Juxtaglomerular cell (renin secretion), Macula densa cell of kidney,Peripolar cell of kidney, Mesangial cell of kidney; Metabolism andstorage cells such as Hepatocyte (liver cell), White fat cell, Brown fatcell, Liver lipocyte; Barrier function cells (Lung, Gut, Exocrine Glandsand Urogenital Tract) or Kidney cells such as Kidney glomerulus parietalcell, Kidney glomerulus podocyte, Kidney proximal tubule brush bordercell, Loop of Henle thin segment cell, Kidney distal tubule cell, and/orKidney collecting duct cell; Type I pneumocyte (lining air space oflung), Pancreatic duct cell (centroacinar cell), Nonstriated duct cell(of sweat gland, salivary gland, mammary gland, etc.), principal cell,Intercalated cell, Duct cell (of seminal vesicle, prostate gland, etc.),Intestinal brush border cell (with microvilli), Exocrine gland striatedduct cell, Gall bladder epithelial cell, Ductulus efferens nonciliatedcell, Epididymal principal cell, Epididymal basal cell; Epithelial cellslining closed internal body cavities such as Blood vessel and lymphaticvascular endothelial fenestrated cell, Blood vessel and lymphaticvascular endothelial continuous cell, Blood vessel and lymphaticvascular endothelial splenic cell, Synovial cell (lining joint cavities,hyaluronic acid secretion), Serosal cell (lining peritoneal, pleural,and pericardial cavities), Squamous cell (lining perilymphatic space ofear), Squamous cell (lining endolymphatic space of ear), Columnar cellof endolymphatic sac with microvilli (lining endolymphatic space ofear), Columnar cell of endolymphatic sac without microvilli (liningendolymphatic space of ear), Dark cell (lining endolymphatic space ofear), Vestibular membrane cell (lining endolymphatic space of ear),Stria vascularis basal cell (lining endolymphatic space of ear), Striavascularis marginal cell (lining endolymphatic space of ear), Cell ofClaudius (lining endolymphatic space of ear), Cell of Boettcher (liningendolymphatic space of ear), Choroid plexus cell (cerebrospinal fluidsecretion), Pia-arachnoid squamous cell, Pigmented ciliary epitheliumcell of eye, Nonpigmented ciliary epithelium cell of eye, Cornealendothelial cell; Ciliated cells with propulsive function such asRespiratory tract ciliated cell, Oviduct ciliated cell (in female),Uterine endometrial ciliated cell (in female), Rete testis ciliated cell(in male), Ductulus efferens ciliated cell (in male), and/or Ciliatedependymal cell of central nervous system (lining brain cavities); cellsthat secrete specialized ECMs, such as Ameloblast epithelial cell (toothenamel secretion), Planum semilunatum epithelial cell of vestibularapparatus of ear (proteoglycan secretion), Organ of Corti interdentalepithelial cell (secreting tectorial membrane covering hair cells),Loose connective tissue fibroblasts, Corneal fibroblasts (cornealkeratocytes), Tendon fibroblasts, Bone marrow reticular tissuefibroblasts, Other nonepithelial fibroblasts, Pericyte, Nucleus pulposuscell of intervertebral disc, Cementoblast/cementocyte (tooth rootbonelike cementum secretion), Odontoblast/odontocyte (tooth dentinsecretion), Hyaline cartilage chondrocyte, Fibrocartilage chondrocyte,Elastic cartilage chondrocyte, Osteoblast/osteocyte, Osteoprogenitorcell (stem cell of osteoblasts), Hyalocyte of vitreous body of eye,Stellate cell of perilymphatic space of ear, Hepatic stellate cell (Itocell), Pancreatic stellate cells; contractile cells, such as Skeletalmuscle cells, Red skeletal muscle cell (slow), White skeletal musclecell (fast), Intermediate skeletal muscle cell, nuclear bag cell ofmuscle spindle, nuclear chain cell of muscle spindle, Satellite cell(stem cell), Heart muscle cells, Ordinary heart muscle cell, Nodal heartmuscle cell, Purkinje fiber cell, Smooth muscle cell (various types),Myoepithelial cell of iris, Myoepithelial cell of exocrine glands; Bloodand immune system cells, such as Erythrocyte (red blood cell),Megakaryocyte (platelet precursor), Monocyte, Connective tissuemacrophage (various types), Epidermal Langerhans cell, Osteoclast (inbone), Dendritic cell (in lymphoid tissues), Microglial cell (in centralnervous system), Neutrophil granulocyte, Eosinophil granulocyte,Basophil granulocyte, Mast cell, Helper T cell, Suppressor T cell,Cytotoxic T cell, Natural Killer T cell, B cell, Natural killer cell,Reticulocyte, Stem cells and committed progenitors for the blood andimmune system (various types); Nervous system cells, Sensory transducercells such as Auditory inner hair cell of organ of Corti, Auditory outerhair cell of organ of Corti, Basal cell of olfactory epithelium (stemcell for olfactory neurons), Cold-sensitive primary sensory neurons,Heat-sensitive primary sensory neurons, Merkel cell of epidermis (touchsensor), Olfactory receptor neuron, Pain-sensitive primary sensoryneurons (various types); Photoreceptor cells of retina in eye includingPhotoreceptor rod cells, Photoreceptor blue-sensitive cone cell of eye,Photoreceptor green-sensitive cone cell of eye, Photoreceptorred-sensitive cone cell of eye, Proprioceptive primary sensory neurons(various types); Touch-sensitive primary sensory neurons (varioustypes); Type I carotid body cell (blood pH sensor); Type II carotid bodycell (blood pH sensor); Type I hair cell of vestibular apparatus of ear(acceleration and gravity); Type II hair cell of vestibular apparatus ofear (acceleration and gravity); and/or Type I taste bud cell; Autonomicneuron cells such as Cholinergic neural cell (various types), Adrenergicneural cell (various types), Peptidergic neural cell (various types);sense organ and peripheral neuron supporting cells, such as Inner pillarcell of organ of Corti, Outer pillar cell of organ of Corti, Innerphalangeal cell of organ of Corti, Outer phalangeal cell of organ ofCorti, Border cell of organ of Corti, Hensen cell of organ of Corti,Vestibular apparatus supporting cell, Type I taste bud supporting cell,Olfactory epithelium supporting cell, Schwann cell, Satellite cell(encapsulating peripheral nerve cell bodies), Enteric glial cells;central nervous system neurons and glial cells such as Astrocyte(various types), Neuron cells (large variety of types, still poorlyclassified), Oligodendrocyte, and Spindle neuron; Lens cells such asAnterior lens epithelial cell and Crystallin-containing lens fibercells; pigment cells such as melanocytes and retinal pigmentedepithelial cells; and germ cells, such as Oogonium/Oocyte, Spermatid,Spermatocyte, Spermatogonium cell (stem cell for spermatocyte), andSpermatozoon; nurse cells; Ovarian follicle cells; Setoli cell (intestis); Thymus epithelial cells; and interstitial cells such asinterstitial kidney cells.

Implementation 37.

The metamaterial scaffold according to any one of implementations 26-36,wherein the plurality of biological cells comprises cardiomyocytes.

Implementation 38.

The metamaterial scaffold according to any one of implementations 26-37,wherein the lumen has a diameter between about 0.005 mm and about 50 mm.

Implementation 39.

A microfluidic device comprising a metamaterial scaffold according toany one of implementations 26-38.

Implementation 40.

The microfluidic device of implementation 36, further comprising a valveof any one of implementations 1-20 in fluid communication with themetamaterial scaffold.

Implementation 41.

The microfluidic device of implementation 39, comprising a first portand a second port, the first port being in fluid communication with themetamaterial scaffold via a first channel portion, the second port beingin fluid communication with the metamaterial scaffold via a secondchannel portion; a first valve disposed in the first channel portion;and a second valve disposed in the second channel portion, wherein thefirst valve and the second valve are configured to cause unidirectionalflow through the metamaterial scaffold.

Implementation 42.

The microfluidic device of implementation 39, comprising a main channelin fluid communication with the metamaterial scaffold, the microfluidicdevice further comprising a first port and a second port, the first portbeing in fluid communication with the main channel via a first channelportion, the second port being in fluid communication with the mainchannel via a second channel portion; a first valve disposed in thefirst channel portion; and a second valve disposed in the second channelportion.

It is contemplated that any element or any portion thereof from any ofimplementations 1-42 above can be combined with any other element orelements or portion(s) thereof from any of implementations 1-42 to forman implementation of the present disclosure.

Some of the embodiments will be more readily understood by reference tothe following examples, which are included merely for purposes ofillustration of certain aspects and embodiments of the presentinvention, and should not be construed as limiting. As such, it will bereadily apparent that any of the disclosed specific constructs andexperimental plan can be substituted within the scope of the presentdisclosure.

EXAMPLES

Scaffold-Based Ventricular Microfluidic Model

An in vitro ventricular model needs to be structurally stable and toproduce measurable contractile output. Structural stability of the invivo myocardium is established by the passive tensile stress produced byits elastic extracellular matrix and by the pressure within the cardiacchambers. An in vitro scaffold should thus be able to incorporate suchtensile forces. The need for such a scaffold is shown with reference toFIG. 15A and FIG. 15B which shows a channel portion 360 and cardiactissue 312, such as a first 360A or second 360B channel portion with acardiac tissue 312 configured as shown in FIG. 7. The heart tube modelis shown one day after seeding, 15A, and 7 days, 15B, after seeding,demonstrating the effect of matrix compaction in the absence of amechanical support. The construct began collapsing a couple of days'post seeding due to the cell-mediated compaction of the extracellularmatrix, blocking the channel, halting fluid displacement uponcontraction and obstructing media flow and nutrient exchange. Eventuallythe tissue turned necrotic and did not beat.

Moreover, the native myocardium is organized in aligned, anisotropicmyocardial fibers and output maximization relies on the directionalcontraction of cardiomyocytes. Such anisotropy can be achieved in vitroby exposing the cardiac tissue to anisotropic ECM architecture oranisotropic mechanical stiffness, causing cardiomyocyte alignment andelongation. A mechanically anisotropic scaffold could therefore improvecontractile output.

Additionally, the in vivo myocardium utilizes multiple layers of thickmyocardial musculature to produce the observed powerful contractions. Invitro models cannot utilize muscular thickness to generate output, astissues beyond 300 μm thickness require perfusion throughvascularization that has yet to be achieved in in vitro cardiac tissues.Engineering scaffolds to enhance output beyond cellular anisotropy canprovide sufficient, measurable cardiac output in vitro in the absence ofvasculature.

To address these issues, TPDLW was used to fabricate a scaffold with (1)specified geometry to produce concave cardiac tissue, (2) specifiedmechanical stiffness to preserve tissue structure, (3) mechanicalanisotropy to induce tissue alignment and improvement contractility and(4) auxetic properties to promote chamber volume reduction upon cellularcontraction. In addition, a protocol to seed cardiac tissue on theresulting scaffold and a microfluidic system to monitor and measure thecontractile performance of the seeded tissue can be implemented.

Experimental

Existing data on the μTUG (Hinson, J. T. et al. Science (80-.), 349,982-986 (2015)) cardiac tissue system can be used to calculate thestatic force exerted by cardiac tissue and estimate an approximation ofthe required passive stiffness of the scaffold. Reported auxetic cellunits, such as the inverted hexagon (FIGS. 12A and 12B), can be utilizedto form a cylindrical auxetic scaffold. FEM simulations (COMSOLMulti-physics) can be used to calculate each scaffold design'smechanical properties and the design can then be iterated to achieve theestimated mechanical requirements. The scaffold can be printed withTPDLW to accurately replicate its simulated geometrical features. TPDLWrequires submerging the printed scaffold in solvents whose surfacetension might exceed the yield stress of the scaffold and thereforecrush the scaffold upon drying. In such an event, Critical Point Drying(CPD) (DCP-1, Denton) can be used to dry the scaffold.

To accelerate the scaffold development cycle, results from mechanicalcharacterization can be used to calibrate the simulation results,allowing design iteration to be accomplished largely by simulations. Thephotoresist IP-S(Nanoscribe GmbH) can be used, as it provides sufficientresolution to print the expected features of the scaffold, but allows ahigher print speed to accelerate the printing process. Rectangularblocks of IP-S of 300×300×10 μm dimensions (L×W×H) can be printed andsubjected to a compression test with nanoindentation (HysitronTriboindenter) to measure the mechanical properties of IP-S. A tensiletest on springs printed on electrostatic comb drivemicro-electromechanical system (MEMS) devices can be used as previouslyreported (J. R. K. Stark et. al., Adv. Mater. Technol. 3, 1-6 (2018)) toapply strain on microscopic spring of IP-S to measure the mechanicalproperties of IP-S under tension. To verify the compression and tensilemeasurements, nanoindentation can be used to extract the stress-straincurve of an IP-S beam using a cantilever deflection test and can becompared to the curve generated by the equivalent in silico model.Finally, nanoindentation can be used to measure the force-displacementcurve of the scaffold, its Poisson ratio and its resilience to fatigue,which will verify the corresponding simulation results.

PDMS molding can be used to fabricate the microfluidic system. Theprinted scaffold can be placed at the entrance of the microfluidicchannel, and can be seeded using an adaption of the existing seedingprotocols for the μTUG system. Particle Image Velocimetry can be used toestimate the volume changes of the cell-laden scaffold and the pressurefluctuations due to the tissue contractions.

Results

Scaffolds were printed with TPDLW using photoresist IP-S(Nanoscribe). Ahollow cylindrical construct 1602 based on the inverted hexagon cellunit was designed and printed as shown in FIG. 16A. Region 1604 showsthe auxetic scaffold, and region 1606 shows a rectangular lattice thatforms part of the scaffold and is designed to serve as a fixedattachment structure for the tissue and to facilitate insertion of theconstruct onto a microfluidic channel by way of cylindrical stem 1608.The scale bar for FIG. 16A is 500 μm. FIG. 16B shows a detailed sectionof the auxetic scaffold, where the scale bar shows 100 μm. In both FIGS.16A and 16B, the line 1610 is added to help guide the eyes, and does notnecessarily form a part of the construct. FEM simulations were used tovalidate the auxetic behavior of the scaffold.

The mechanical and auxetic properties of the scaffold were also probedusing nanoindentation. FIG. 17A shows the auxetic mesh under compressionduring a nanoindentation test, where the scale bar is 200 μm. Theminimum diameter 1712 and initial diameter 1714 are indicated by doubleheaded arrows. FIG. 17B shows the force-displacement curve for ananoindentation test. The scaffold demonstrates non-linear stress-straincurves with an initial stiffer linear regime followed by a softersemi-linear regime. The initial linear modulus is estimated at 3 kPa.Ideally, the static compaction force should be absorbed by the stifflinear regime, and the dynamic contractile force will be exerted on thesoft non-linear regime, minimizing simultaneously the volume loss due tocompaction and the resistance to the contractile force.

PDMS microfluidic devices were then designed and implemented as shown inFIGS. 18A-18I. FIG. 18A shows an initial microfluidic device prior toaddition of the auxetic construct. A protocol to add the printedconstruct to the microfluidic device and seed this with cells is shownby the detailed views of FIG. 18B-18H, which creates a hollowcylindrical cap of cardiac tissue supported by the auxetic mesh andattached to the end of the main channel 1802 of the microfluidic device.The microfluidic device after addition of the auxetic construct is shownby FIG. 18I, illustrating tissue 1850 in well 1810 that ismicrofluidically connected to the large major channel 1802 thatcommunicates through small minor channels 1804 and 1805 housing thevalves (not shown here) with wells 320 and 310 whose hydrostaticpressure can be controlled.

Therefore, in additional detail: FIGS. 18A and 18B shows the initialmicrofluidic PDMS device consists of a network of microfluidic channelsthat connect 3 wells. The first circular well 320 and second well 330are configured to house liquid columns to regulate the pressureexperienced in the third well 1810 designed as a chamber for housing thetissue 1850. In a first step, FIG. 18C, of the seeding protocol, thescaffold 1602 is inserted in the tissue well 1810 and fixed at the endof the channel 1802. FIG. 18D shows a second step where a needle 1808 isinserted to occupy the cavity of the scaffold 1602. The tissue well 1810is in a third step filled with a liquid solution 1820 containing cellsand extracellular matrix as shown by FIG. 18E. FIG. 18F shows a fourthstep where the matrix gels and is compacted by the cells, forming acell-laden layer 1850 around the needle. The needle is removed in afifth step, leaving behind a cavity, FIG. 18G. In the final, sixth, stepshown by FIG. 18H the redundant channels are sealed, producing a closedmicrofluidic system.

A similar seeding protocol as described here can be used to make anyconstruct described in this disclosure. For example, the microfluidicdevices as shown and described with reference to FIG. 8A-8F or FIG.9A-9B, where the tissue is supported with an extracellular matrix suchas the scaffold 1602, can be made. For example, the scaffold 1602 couldfurther include a second rectangular mesh similar to 1606 and positionedat indicating line 1610, for attachment to a second cylindrical stemsimilar to cylindrical stem 1608.

Validation of Ventricular Properties and Investigation of Load-FunctionRelation.

Current in vitro models fail to replicate the pressure and volumeconditions of the ventricle, and its derivative measures ofcontractility, compliance and ejection fraction. The classification ofheart failure (HF) into HF with preserved ejection fraction and into HFwith reduced ejection fraction is a prime example of the significance ofsuch measures. A system that uses the valves and metamaterial supportedtissues as described herein can be assembled to provide a system torecapitulate the Left Ventricular Pressure Volume Loop (PV loop). Thissystem can recapitulate the myocardial response to establishedpharmacological, electrical and mechanical modulators thoughpressure-volume measurements. The system can also be used to probe theeffect of increased preload and afterload on tissue performance andremodeling.

Experimental

The sub-pascal valves, such as valves 100 (FIGS. 1A-1C) and 200 (FIGS.6A and 6B) can be added to the minor channels 1805 and 1804 of amicrofluidic system, such as the system shown by (FIG. 18I). The abilityof the tissue to regulate the valves, the emergence of unidirectionalflow from one well to the other and the presence of a PV loop withoutthe isovolumetric phases can be confirmed. Glass columns can be added tothe wells to control the pressure in the wells through liquid additionand removal, thereby differentiating the preload and afterloadpressures. The afterload can be increased to replicate the PV loop withall 4 phases included.

The acute response of the cardiac tissue with potent modulators ofcontractile performance such as isoproterenol (adrenergic agonist:Novak, A. et al. J. Cell. Mol. Med. 16, 468-482 (2012)) and carteolol(non-selective adrenergic antagonist), carbachol (cholinergic agonist),digoxin (Na⁺/K⁺ ATPase inhibitor), Verapamil/Nifedipine (L-type Ca²⁺channel inhibitor: Nunes, S. S. et al. Nat. Methods 10, (2013)),disopyramide/flecainide (Na⁺ channel inhibitor)¹³, caffeine (ryanodinereceptor agonist) and doxorubicin (cardiotoxic chemotherapeutic agent:Pai, V. B. et. al., Drug Sal. 22, 263-302 (2000)) can be demonstrated.The response to such modulators through their effect on the PV loopoutputs can be quantified. Furthermore, the tissues can be electricallypaced with increasing frequency to demonstrate the force frequencyresponse in the PV loop metrics. The preload pressure will also beacutely increased to demonstrate the Frank Starling mechanism.

To investigate the effects of load changes on cardiac performance, thetissues can first be allowed to mature under constant 1 Hz stimulation.μTUG data from previous experiments show that 10 days are required forthe tissue output to stabilize. Therefore, starting day 11, a comparisoncardiac performance under a permanently increased preload and/orafterload can be made. The performance of the tissue can be monitoreddaily until a statistically significant difference in ejection fractionis observed, or up to a set amount of days, such as up to 14 days. RNAsequencing can be used to quantify transcriptome. Gene expressionchanges can be compared to control tissues and to data from in vivostudies. In parallel, cellular shape and size through membrane stainingwith wheat germ agglutinin and sarcomeric structure through α-actinin2staining can be used to evaluate the effect of load on the cells. Forstatistical analysis of the PV loops, gene expression, cellular andsarcomeric metrics data can be evaluated using analysis of variance(ANOVA) with significance at 95% confidence intervals, p-value <0.05.

What is claimed is:
 1. A valve comprising: a body including an innerbore extending between a first port and a second port, a seat, and oneor more restrainers; and a disk including a cylindrical portion and aspherical portion, the disk being moveable between the seat and the oneor more restrainers and being configured such that (i) a first pressurethat is less than 1 pascal and applied in a first direction causes thedisk to move from a first position towards a second position to permitfluid communication between the first port and the second port and (ii)a second pressure that is less than 1 pascal and applied in a secondopposing direction causes the disk to move from the second positiontowards the first position to inhibit fluid communication between thefirst port and the second port.
 2. The valve of claim 1, wherein thefirst pressure and the second pressure are less than 0.5 pascals.
 3. Thevalve of claim 1, wherein the first pressure is between about 0.1pascals and about 0.5 pascals.
 4. The valve of claim 1, wherein thesecond pressure is between about 0.05 pascals and about 0.2 pascals. 5.The valve of claim 1, wherein the disk is moveable such that the firstpressure causes the disk to move from the first position to the secondposition in less than 500 milliseconds.
 6. The valve of claim 1, whereinthe body is cylindrical and has a first diameter is that is 400 micronsor less and a longitudinal length that is 1110 microns or less, and theinner bore is cylindrical and has a second diameter that is 300 micronsor less.
 7. The valve of claim 1, wherein a distance between the diskand the one or more restrainers is between about 10 microns and about 30microns responsive to the disk being in the second position.
 8. Thevalve of claim 1, wherein the body is rigid.
 9. The valve of claim 1,wherein the body is monolithic.
 10. The valve of claim 1, wherein aportion of the spherical portion of the disk contacts the seatresponsive to the disk being in the first position to aid inhibitingfluid communication between the first port and the second port.
 11. Thevalve of claim 1, wherein the spherical portion of the disk has a degreeof curvature that is between about 30 degrees and about 60 degrees. 12.The valve of claim 1, wherein a distance between the first port and theseat is between about 5% and about 15% of a longitudinal length of thebody.
 13. A microfluidic system comprising: a valve including: a bodyincluding an inner bore extending between a first port and a secondport, a seat having an opening and being disposed within the inner bore,and a plurality of restrainers positioned between the seat and thesecond port; and a disk configured to move relative to the seat and theplurality of restrainers such that application of a first predeterminedpressure that is between about 0.05 pascals and 1 pascal causes the diskto move from a first position towards a second position to permit fluidcommunication between the first port and the second port.
 14. The valveof claim 13, wherein the disk inhibits fluid communication between thefirst port and the second port responsive to being in the firstposition.
 15. The valve of claim 14, wherein a spherical portion of thedisk is partially disposed within the opening of the seat to aid ininhibiting fluid communication between the first port and the secondport responsive to the disk being in the first position.
 16. The valveof claim 14, wherein the disk is moveable such that application of asecond predetermined pressure causes the disk to move from the secondposition towards the first position to inhibit fluid communicationbetween the first port and the second port.
 17. The valve of claim 16,wherein the first predetermined pressure is different than the secondpredetermined pressure.
 18. The valve of claim 13, wherein the diskincludes a spherical portion and a cylindrical portion having a firstdiameter that is less than a second diameter of the inner bore.
 19. Thevalve of claim 18, wherein a third diameter of the opening of the seatis equal to or smaller than twice the first diameter minus the seconddiameter.
 20. The valve of claim 13, wherein the body is monolithic.